DALLAS (AP) — The FBI is investigating allegations that Texas Attorney General Ken Paxton broke the law in using his office to benefit a wealthy donor, according to two people with knowledge of the probe.

Federal agents are looking into claims by former members of Paxton’s staff that the high-profile Republican committed bribery, abuse of office and other crimes to help Austin real estate developer Nate Paul, the people told The Associated Press. They insisted on anonymity to discuss the investigation because it is ongoing.

Confirmation of the criminal probe marks mounting legal peril for Paxton, who’s denied wrongdoing and refused calls for his resignation since his top deputies reported him to federal authorities at the end of September.

A criminal defense attorney for Paxton, Philip Hilder, declined to comment. Spokespersons in the attorney general’s office did not immediately respond to requests for comment.

It’s unclear how far the FBI is into investigating the allegations against Paxton. An agency spokeswoman in San Antonio declined to comment.

Paxton is accused of using his position as Texas’ top law enforcement official to benefit Paul in several ways, according to seven senior lawyers in the attorney general’s office and the agency’s head of law enforcement. Central to their claims is the fact that Paxton hired an outside lawyer to investigate the developer’s allegations that the FBI improperly searched his home and offices last year.

Each of Paxton’s accusers has resigned, been put on leave or been fired since reporting him. Last week, four of them filed a state whistleblower lawsuit against the attorney general, claiming he ousted them as retribution.

The full nature of Paxton and Paul’s connection remains unclear. In 2018, Paul donated $25,000 to the attorney general’s reelection campaign. The developer also said in a recent deposition that Paxton recommended a woman for her job with his company.

Two people previously told The Associated Press that Paxton acknowledged in 2018 having an extramarital affair with the woman, who was then a state Senate aide. The people spoke on condition of anonymity due to fears about retaliation.

Paxton said in a Tuesday statement to the Austin American-Stateman that, “after reviewing the claims made by former employees of this office, their allegations are overblown, based upon assumptions, and to a large degree misrepresent the facts.”

Paxton has spent most of his tenure in office maintaining his innocence in the face of an indictment on unrelated securities fraud charges. The case has been stalled for years over legal challenges.