Representative George Santos, the New York Republican who has been the target of numerous investigations into his personal and campaign finances since his biography was found to be a web of lies and exaggerations, has been charged by federal prosecutors in New York, three people familiar with the investigation said.

The charges come after months of investigation by the office of the U.S. attorney for the Eastern District of New York, which has been conducting one of the inquiries into Mr. Santos’s financial and campaign activities.

The specific charges against Mr. Santos, 34, are not yet clear. Mr. Santos could appear as soon as Wednesday in federal court, according to CNN, which first reported the charges.

Mr. Santos has been subject to intense scrutiny in the wake of reporting published by The New York Times last year that found he had lied about his biography, education and work history to voters and that raised questions about his personal wealth and campaign finances.

Subsequent reporting uncovered evidence of possible misconduct, including an unregistered fund that purported to be raising huge amounts for Mr. Santos’s campaign seemingly in violation of campaign finance laws; hundreds of thousands of dollars in unexplained spending; and a strange string of payments for $199.99, just below the threshold where receipts would be required.

The F.B.I., federal prosecutors and the Nassau County district attorney’s office have also been investigating Mr. Santos’s role in brokering a $19 million luxury yacht deal between two of his wealthy donors. And the Securities and Exchange Commission has made inquiries into the work that Mr. Santos did for the troubled financial firm Harbor City Capital, which the government accused of operating as a Ponzi scheme.

Mr. Santos is also facing separate charges in Brazil on an allegation of check fraud; a hearing on that matter will take place on Thursday.

Mr. Santos, his lawyer and a spokeswoman in his Washington office did not immediately respond to messages seeking comment. The Justice Department and the F.B.I. declined to comment, and a spokesman for the U.S. attorney’s office in Brooklyn could not be reached.

While Mr. Santos has admitted to falsifying much of his résumé and exaggerating other claims, the congressman has stood by other apparent fabrications and has denied any criminal wrongdoing. He has also maintained innocence regarding questions about his campaign finances, saying that the responsibility for those filings rests with his campaign treasurer, Nancy Marks. A lawyer for Ms. Marks, Ray Perini, declined to comment on Tuesday evening.

Mr. Santos, who was elected in November to represent a district that includes parts of Long Island and Queens, has insisted that he would not step aside despite the mounting pressure coming from several investigations and numerous calls from his House colleagues for him to resign.

The timeline for any case against Mr. Santos is still unknown. But even if Mr. Santos was convicted of a crime, he could continue to serve in Congress. He would only be removed from office if two-thirds of the members of the House of Representatives voted to expel him.

Speaker Kevin McCarthy of California, who is overseeing an exceedingly tight Republican majority, said he would call for Mr. Santos to resign if he was found guilty, but not before.

Mr. McCarthy noted that he had already asked the congressman not to serve on committees, but said that Mr. Santos deserved a right to fight the charges like other lawmakers who had been charged in the past.

“We will just follow the same pattern we always have,” he said. “If a person is indicted, they are not on committees, they have the right to vote but they have to go to trial.”

“In America, you are innocent until proven guilty,” he added.

Some of Mr. McCarthy’s Republican colleagues, however, were less generous in their views of Mr. Santos. Already, about a dozen Republicans have joined numerous Democrats in demanding that Mr. Santos resign. Many of them doubled down on their calls for action on Tuesday.

“There’s a clock ticking, and George Santos should have resigned in December,” Representative Marc Molinaro, a Republican of New York, said. “He should have resigned in January. He should have resigned yesterday, and maybe he’ll resign today. But sooner or later, honesty and justice will be delivered.”

Mr. Santos did not take part in two votes in the House on Tuesday night. Staffers in his Washington office were abruptly told to go home that evening without explanation and to work from home on Wednesday, a person familiar with the office said.

Mr. McCarthy has for months pinned Mr. Santos’s fate in Congress on the results of an investigation by the House Ethics Committee. The committee, split evenly between Democrats and Republicans, has been investigating whether Mr. Santos failed to properly fill out his financial disclosure forms, violated federal conflict of interest laws or engaged in other unlawful activity during his 2022 campaign.

Last month, Mr. Santos announced he would seek re-election. “I’m not going anywhere,” he later told a group of Republicans at an event in Washington. “You’re going to have to drag my dead, cold body out of this institution.”

Reporting was contributed by Nicholas Fandos in New York, and Catie Edmondson, Glenn Thrush and Luke Broadwater in Washington.