Just minutes before the cargo ship Dali was set to glide under Baltimore’s Francis Scott Key Bridge, the ship’s alarms began to blare. The lights went out. The engine halted. Even the rudder, which the crew uses to maneuver the vessel, was frozen.

As a frantic effort to restore the ship was underway, the pilot soon recognized that the aimless vessel was drifting toward disaster, and called for help.

The cascading collapse of the vessel’s most crucial operating systems left the Dali adrift until it ultimately collided with the Key bridge, knocking the span into the river and killing six people. But as crews this week were still sorting out how to disentangle the ship and recover the bodies of those who died, investigators were also turning to the most central question: What could have caused such a catastrophic failure at the worst possible moment?

Engineers, captains and shipping officials around the world are waiting for that answer in an era when the industry’s largest ships can carry four times as much cargo as those just a few decades ago, navigating through congested urban ports under bridges that may carry tens of thousands of people a day,

Already, a few key questions are emerging, according to engineers and shipping experts monitoring the investigation, and most of them point to the electrical generators that power nearly every system on the 984-foot vessel, not only the lights, navigation and steering, but the pumps that provide fuel, oil and water to the massive diesel engine.

The “complete blackout” reported by the pilot is hard to explain in today’s shipping world, in which large commercial vessels now operate with a range of automation, computerized monitoring, and built-in redundancies and backup systems designed to avert just such a calamity.

“In the last 30 to 40 years, the level of that redundancy has been increasing quite considerably,” said John Carlton, a professor of marine engineering at City, University of London. “The ship of today is so very different to the one of 30 years ago.”

Yet there is a wide range of possible factors contributing to the failure that investigators will have to sift through as they interview crew members, examine fuel supplies and scrutinize the ship systems that broke down that night.

If there was faulty maintenance, it could have caused a delay in starting the emergency backup generator, or an electrical fault could have prevented it from remaining engaged. Contaminated fuel or an inadvertently closed valve could have fouled or starved the main generators. Human error could have set off problems or failed to overcome them. The ship’s own automation could have led to equipment glitches. Or a fire could have broken out and damaged crucial equipment.

The answers will have implications not only for international shipping but also for who is liable for damages that S&P Global Ratings estimated at more than $2 billion.

Grace Ocean Private, the Singapore-based company that owns the Dali, said it was “fully cooperating with federal and state government agencies.” Grace Ocean’s owner is Yoshimasa Abe, a Japanese citizen who owns at least two shipping lines and more than 50 vessels, including some of the world’s biggest container ships. While the Dali was insured, Mr. Abe’s company potentially faces large claims against it, depending on the findings of the accident investigators.

Given the scope of the failure, it is possible that there were multiple problems. Timothy McCoy, a professor specializing in marine engineering at the University of Michigan, said that much like a plane crash, an extensive breakdown of a ship’s systems typically involves a sequence of events.

A close look at the potential factors would include many of the most essential elements in the operation of a modern cargo vessel — including the fuel that feeds the ship’s 55,000-horsepower diesel engine that in turn powers the ship’s propeller.

Fuel also powers the huge generators that provide electricity to container ships. And a ship like the Dali needs electrical power to run its main engine — its fuel injectors are electrically powered, for instance — and steer its rudder. Without electricity, the ship can go adrift.

An outbreak of contaminated fuel led to reported problems with 32 vessels from Texas to Singapore last August, maritime industry officials reported, with some of them reporting loss of power and propulsion at sea.

In Washington State last year, a large passenger ferry ran aground after losing power as a result of bacterial and fungal growth in the vessel’s fuel tanks that fouled the ship’s filtration systems.

At the time it was built, 2015, the Dali had four generators, according to S&P Maritime Portal, a shipping data service. Not all of them run at once, usually, but container vessels leaving port will typically have an extra generator running, to provide reserve power if needed. “At least two should be online at the same time,” said Mark Bulaclac, an academic on maritime issues who has also served as an engineer on container ships.

If all generators were running on a common source of bad fuel, that might have caused them all to fail.

Henry Lipian, a forensic crash investigator who previously worked in the Coast Guard, said the sudden loss of the ship’s generators led him to think of fuel problems as a potential culprit.

He said investigators would need to look at the fuel on board, how it was delivered, whether it had been tested beforehand and what filtration systems were on the ship. But he said that a problem with the fuel valves could be another explanation.

“I’d want to start tracing all of those fuel lines,” he said.

In Baltimore, investigators were in the process of collecting a fuel sample from the Dali in order to examine the quality, viscosity and signs of any contaminants, said Jennifer Homendy, the chair of the National Transportation Safety Board.

Yet other experts said there were also reasons to doubt the contaminated fuel scenario. New fuels typically undergo testing, and duplicate filtration systems can help clean out problematic components that were not flagged in testing. No reports have emerged of other ships having a problem from the same batch of fuel.

Maritime engineers say an electrical chain reaction could also have caused all the generators to go down. When one generator fails, it can create a situation in which there is too much demand for too little supply of electricity. Other generators are then at risk of being damaged, so the system will shut them down, too, said Richard Burke, a professor of naval architecture and marine engineering at SUNY Maritime College in New York.

“It’s as if you and I are both holding up a heavy weight and I let go,” he said, “You can’t hold it by yourself, so you drop the weight.”

A haywire generator could also zap the electrical distribution system on the ship, said Capt. Morgan McManus, an instructor at SUNY Maritime College.

When all the main generators fail, ships rely on a backup generator that is typically situated above the water line in another area of the ship, with its own fuel source.

Marine engineers say backup generators provide electricity to run some lights, the navigation system — and, crucially, the ship’s steering system. Without at least backup power, the rudder cannot be moved.

Because some lights came back on after the Dali experienced its initial blackout, it appears the backup generator did activate, but only after a roughly one-minute delay. Even then, the lights appeared to go back off, then on again, raising the possibility of a problem with the backup generator.

Ms. Homendy of the N.T.S.B. said this week that investigators had collected data “consistent with a power outage” but were still trying to determine the extent.

Clay Diamond, the head of the American Pilots’ Association, a trade group that has been in close contact with the harbor pilots in Maryland, said that steering was restored after the emergency generator came online. But even with a hard turn to the left and the dropping of an anchor, there was not enough time to turn or stop the ship.

Mr. Bulaclac, the shipping engineer, said backup generators are meant to be regularly tested by turning them on for two hours once a month. “What I would like to know is when that emergency diesel generator was last tested,” he said.

The Coast Guard inspected the Dali when it docked in the Port of New York in September but found no deficiencies on the ship. The Coast Guard did not provide details of what it inspected.

The modernization of ships may have introduced other ways vessels can fail. They have increasingly depended on computers to monitor for troubles and take action when a problem is identified. In some ways, this is a built-in layer of automatic protection: If one component gets overloaded, it can be automatically shut down to prevent further damage. But those shutdowns can cause problems on their own.

“I could not rule out that some computer failure shut all the valves off or shut off pumps that provide the fuel,” Mr. Lipian said.

Michael Forsythe and Jenny Gross contributed reporting.