WARREN, Pa. (AP) — Authorities searching for an inmate described by police as “very dangerous” who used bed sheets to escape from a northwestern Pennsylvania jail say they believe he is still in the area and have found stockpiles or campsites in the woods he may have been using.

Michael Burham, 34, who fled the Warren County Prison late Thursday by climbing on exercise equipment and using bed sheets to escape through a window, was a suspect in a homicide investigation and had been held on $1 million bail on kidnapping, burglary and other charges, authorities said.

“We have located small stockpiles or campsites in wooded areas in the general vicinity of Warren, and we believe that at least some of those may be associated with Burham,” Lt. Col. George Bivens of the Pennsylvania State Police told reporters Sunday afternoon at Youngsville Fire Hall.

Warren city police have said Burham “was also associated with the prior carjacking and kidnapping of a local couple while trying to escape capture” and “is considered very dangerous.”

The search by local, multistate and federal authorities has included numerous residences, abandoned structures and wooded areas using K-9 units and aerial resources such as drones and aircraft, authorities said.

Bivens said officials “have no reason to believe he has left the area,” but he noted that authorities are “constantly re-evaluating” that conclusion.

Bivens told WGRZ-TV that Burham has “self-taught survival training” as well as military reserve training. He said the search is taking place in a very large area with a lot of difficult terrain that has cabins and oil and gas sheds and shacks that could offer a fugitive a place to hide.

Officials are also concerned that he “may be receiving assistance” from someone, he said.

The city of Warren announced that its playground program would be closed Monday amid the manhunt, and the county school district said all summer programming at Beaty Warren Middle School would be canceled, including summer food service and meal prep at all city playground sites.

State police urged residents to be vigilant and to keep doors and windows locked. Bivens urged them not to “leave things out where he could supply himself with food, clothes, car, for that matter even a weapon.”

The U.S. Marshals Service was offering a $7,500 reward for information leading to Burham’s capture, and Crime Stoppers was offering $2,000, Bivens said.

“Anyone in this situation becomes more desperate over time, and we plan to use that to our advantage,” Bivens said, adding that “if he’s out here in the woods, we’ll continue to push hard. He’s not going to be able to get a lot of rest. We’re going to push hard until we find him.”

Warren County Sheriff Brian Zeybel told WKBW-TV that he doesn’t believe Burham is “a master of this game” but probably is able to tolerate “a little more discomfort than you or I.” He echoed the state police’s call for residents to take steps to keep themselves safe and to prevent Burham from gaining help or refuge.

“There’s probably houses in this wonderful, beautiful community that the doors haven’t been locked in 40 years, maybe 50 years,” he said. “People leave keys in their car when they pump gas, stuff like that. Hometown rural America, but unfortunately people exploit that. And I don’t want to make it easy for this man to get a car to get a firearm especially and/or just have shelter in a basement or an unlocked shed or something like that.”