Federal prosecutors and the F.B.I. are investigating whether Senator Robert Menendez or his wife received unreported gifts of a luxury car and an apartment in Washington from a halal meat company that is also the focus of a criminal inquiry, two people with knowledge of the matter said on Thursday.

The investigation into Mr. Menendez, a Democrat who is the senior senator from New Jersey, is linked to a government search of the meat company’s offices and the home of its president, according to a lawyer who met with prosecutors.

The search followed the Egyptian government’s decision in 2019 to make the company, IS EG Halal of Edgewater, N.J., the sole authorized importer of halal meat into the country from anywhere in the world. The U.S. Department of Agriculture warned that the abrupt change could drive meat prices for Egypt’s 90 million Muslims higher and disrupt the market.

Mr. Menendez, the chairman of the Foreign Relations Committee, has said that he was willing to assist investigators and a spokesman has maintained that the senator is confident the inquiry “will be successfully closed.”

“I am sure it is going to end up in absolutely nothing,” Mr. Menendez said last week to NBC News.

NBC New York News Channel 4 was the first to report the investigation of unreported gifts. Federal officials declined to comment on Thursday evening.

In the 2019 search of IS EG Halal’s office and the home of its president, Wael Hana, officials seized computers, cellphones and documents, according to court records. Mr. Hana, a Christian who emigrated to the United States from Egypt, has acknowledged in court papers that he had no prior experience certifying that meat was prepared according to Islamic law before he began operating his now global company in April 2019.

A spokeswoman for Mr. Hana denied on Thursday that he or the company had provided gifts to Mr. Menendez or his wife, Nadine Arslanian Menendez.

“IS EG Halal was awarded its halal certification contract with Egypt without any assistance whatsoever from Senator Menendez or any other U.S. public official,” the spokeswoman, Ellen Davis, said in a statement.

Ms. Davis said allegations about gifts being provided “by anyone associated with IS EG Halal to Senator Menendez or his wife at all, let alone in exchange for any kind of favorable treatment, are totally without basis.”

Until recently there had been few outward signs of movement in the federal investigation of Mr. Menendez since an initial blitz of subpoenas became public in October. And Mr. Menendez, 69, has continued to raise funds for his expected run next year for a fourth term in the Senate. The investigation is being conducted by federal prosecutors in Manhattan and the New York F.B.I. office.

Two weeks ago, as part of the same investigation, the Manhattan prosecutors subpoenaed documents tied to a bill that has stalled in the New Jersey Legislature that would limit the height of construction projects near the Palisades along the Hudson River. The subpoena asked for any correspondence about the bill from Mr. Menendez, Ms. Menendez or Fred Daibes, one of the region’s most prominent developers, according to a person familiar with its contents who requested anonymity because they were not authorized to discuss the document publicly.

Mr. Daibes pleaded guilty last year to a federal banking crime as part of a negotiated agreement. The arrangement requires no prison time, and his sentencing has been delayed, fueling speculation that he was cooperating with the Menendez investigation.

On Thursday, one of Mr. Daibes’s lawyers, Timothy M. Donohue, said that he had no comment regarding the status of the investigation in the Southern District of New York.

“But I can confirm that Mr. Daibes is absolutely not a cooperating witness in that matter or any other matter,” Mr. Donohue said in an email.

Mr. Menendez and his wife were married in October 2020 in a small ceremony in Queens.

Even before their engagement, the couple had begun traveling together extensively. They received wedding gifts from a who’s who of New Jersey leaders, according to a disclosure report Mr. Menendez filed in May 2021, as is required of federal officials.

In March 2022, Mr. Menendez amended that report to add an asset belonging to his wife: gold bullion bars worth between $100,001 and $250,000.

The senator’s disclosure reports do not include any mention of a Mercedes or an apartment. Mr. Menendez’s Senate spokeswoman, Jennifer Morrill, said that stories that rely on unnamed sources create a “suggestion of impropriety without any facts.”

She did not directly address the claims that the federal inquiry had expanded to include questions about a Mercedes and a Washington apartment. But she said in an email that relying on unnamed sources for such “extreme and damaging claims” was irresponsible, adding that “any such reporting should require legitimate and named sources, or there should be concern about laws being broken.”

Ms. Menendez, who holds a master’s degree in French from New York University, has worked for Fusion Diagnostics, a medical testing facility in New Jersey. She also started a consulting company, Strategic International Business Consultants, in June 2019, according to the disclosure reports and New Jersey business incorporation records.

Ms. Morrill did not address questions about the gold bullion.

Peter P. Paradis, who retired in January from his post as deputy assistant inspector general for investigations at the U.S.D.A.’s Office of Inspector General, said that it was crucial that questions be asked about the halal company’s sudden control of the worldwide flow of halal meat into Egypt.

“If you had a company that now has a global monopoly on anything, then that should be a concern that people should at least ask questions about,” Mr. Paradis said in an interview.

“And I believe that answers should be given.”