The House Committee on Ethics said Thursday that it was extending an investigation into the conduct of Rep. Vern Buchanan (R-Fla.), who has previously come under scrutiny for reimbursements made to his employees for campaign donations.

The announcement by Chairman Jo Bonner (R-Ala.) and ranking member Linda T. Sanchez (D-Calif.) marks another political challenge for Buchanan, the senior Republican fundraiser in the House, who is also facing a separate Justice Department probe.

The focus of the ethics committee’s investigation is unclear, and neither congressional aides nor Buchanan representatives would divulge details Thursday. One aide said the House panel’s probe was unrelated to separate investigations involving contributions to Buchanan’s campaign. 

“The release issued by the House Ethics Committee today is a routine notification,” said Buchanan spokesman Max Goodman. “We are constructively engaged with the House Ethics Committee and are confident that the committee will dismiss this matter. Because of the confidential nature of these proceedings, we can have no further comment at this time.”

The ethics panel began investigating Buchanan in November, based on a referral from the Office of Congressional Ethics, officials said. The office refers a case to the House panel only if “there is a substantial reason to believe the allegations based on all the information then known to the Board,” according to its published rules.

In their announcement Thursday, Bonner and Sanchez said that extending the ethics probe of Buchanan “does not itself indicate that any violation has occurred, or reflect any judgment on behalf of the Committee.” They said the panel will announced “a course of action” by Feb. 6.

The developments come at the same time that new details have emerged about a separate probe by the Federal Election Commission, which identified more than $80,000 in payments made by Buchanan-controlled car dealerships during the 2006 and 2008 election cycles to reimburse employee contributions to the Vern Buchanan for Congress campaign committee.

Federal election laws forbid using “straw donors” to funnel money to a campaign.

Buchanan testified that he was not aware of the reimbursements and did not order them to be made, as alleged by a former business partner.

FEC investigators came “close to supporting a finding” against Buchanan in the case, but pulled back because of “significant concerns” over the credibility of the former partner, according to a January 2011 general counsel’s report, which leaked publicly this week. The FEC voted 5 to 0 to close the case in February.

The counsel’s report chronicled a series of statements by Buchanan that were contradicted by other testimony or evidence, including his claim that he was not tracking the fundraising efforts of dealership employees. FEC attorneys also said they found evidence that “could demonstrate that Buchanan was attempting to conceal his involvement in the reimbursement scheme.”

Buchanan attorney William J. McGinley said in a statement this week that the FEC’s decision to abandon the probe shows “that Congressman Buchanan and the campaign engaged in no wrongdoing.”

Rep. Pete Sessions (R-Tex.), chairman of the National Republican Congressional Committee, said this week that he had confidence in Buchanan, who serves as NRCC’s finance chairman.