Anne Donnelly, the district attorney for Nassau County, said the allegations that have surfaced in recent days regarding Santos were serious.

"The numerous fabrications and inconsistencies associated with Congressman-Elect Santos are nothing short of stunning," Donnelly, a Republican, said in a statement.

"The residents of Nassau County and other parts of the third district must have an honest and accountable representative in Congress," she added. "No one is above the law and if a crime was committed in this county, we will prosecute it."

Brendan Brosh, a spokesperson for Donnelly's office, would not provide any details about lines of the inquiry, or otherwise elaborate.

"We are looking into the matter," he said, when asked about Santos' fabrications.

Santos, whose representatives did not immediately respond to a request for comment, was elected last month in a wealthy district on New York's Long Island. It was a bright spot for Republicans in what was otherwise a lackluster election night for the party.

The race drew outsized attention as both major candidates self-identified as gay, and Santos was the first non-incumbent Republican who identifies as a member of the LGBTQ community to win a seat in the U.S. House.

But reporting by the New York Times and other media outlets in recent weeks called into question almost every element of Santos' life story.

Among other claims, Santos said he had degrees from New York University and Baruch College, despite neither institution having any record of him attending. He claimed to have worked at Goldman Sachs and Citigroup, which was also untrue.

He said falsely that he was Jewish and that his grandparents escaped the Nazis during World War Two, and he failed to disclose that he was married to a woman for several years ending in 2019.

In recent days, Santos has apologized for "embellishing" his resume, while defending aspects of the way he had represented himself.

For instance, he has since described himself as "Jew-ish" rather than "Jewish" when discussing his heritage, telling the New York Post that he described himself that way because his "maternal family had a Jewish background."

The district he is set to represent, which includes parts of Long Island and parts of Queens, is heavily Jewish.

Several congressional Democrats have called on Santos to resign, and he had faced heat from some Republicans as well. Republican leaders, including top House Republican Kevin McCarthy, have remained silent on the issue, however.