NASHVILLE (AP) — Tennessee's Republican House speaker says he and other state lawmakers have been subpoenaed to appear before a federal grand jury in an intensifying federal investigation, following a former lawmaker's guilty plea to wire fraud in an alleged political consulting kickback scheme that implicates the speaker's scandal-plagued predecessor.

In a statement, Speaker Cameron Sexton reiterated he has been "fully cooperating" with federal authorities in the investigation since assuming the top House position in 2019 after Rep. Glen Casada was pressured into resigning from the speaker role.

"It is not unexpected that I and other members would be called to appear before a grand jury to provide factual statements as part of this ongoing investigation," Sexton said in the statement.

Earlier this month, a federal wire fraud charge was unsealed against former Republican Rep. Robin Smith. She quickly resigned and then pleaded guilty a day later, pledging her cooperation with authorities as the investigation unfolds.

Federal authorities say Smith, Casada and his former chief of staff Cade Cothren collaborated on a consulting firm, Phoenix Solutions, as a way to funnel money to themselves secretively and illegally through both campaign and taxpayer-funded work. Prosecutors have so far kept Casada and Cothren unnamed and have not charged them with anything, but they described the two in easily identifiable terms in court documents.

Prosecutors said the three claimed the firm was run by a certain "Matthew Phoenix." In fact, it was Cothren using an alias because they feared lawmakers and the House speaker's office — which Sexton had taken over — would not use the vendor if Cothren's involvement came to light, prosecutors allege.

Casada and Cothren had been pushed into resigning as speaker and chief of staff in 2019 over swirling scandals, including revelations they exchanged sexually explicit text messages about women years beforehand. Casada remains a House lawmaker, though he is not seeking reelection and has announced a run for Williamson County clerk.

State campaign finance regulators, meanwhile, have handed Williamson County prosecutors their investigations into Casada, Cothren and a political action committee named the Faith Family Freedom Fund.

Ahead of the 2020 GOP primary election, the PAC attacked then-Rep. Rick Tillis, the brother of North Carolina U.S. Sen. Thom Tillis. Rick Tillis lost to Republican Rep. Todd Warner. Warner was among those subject to FBI searches at the legislative building and other addresses in January 2021, alongside Casada, Cothren, Smith and others.

The PAC's treasurer testified in January that she is Cothren's former girlfriend and opened the PAC because Cothren asked her to, saying Cothren assured her she was doing nothing wrong and that she took no further action.

Cothren has informed the registry that he is invoking his Fifth Amendment right against self-incrimination.

Casada, who was also subpoenaed, has told the registry he was not involved with the Faith Family Freedom Fund.