U.S. Rep. G.K. Butterfield is one of six members of Congress under investigation for allegedly mishandling travel funds, according to the Wall Street Journal.

Butterfield, D-1st District, was contacted and questioned by the Office of Congressional Ethics about allegedly misusing his congressional travel allowance. An earlier Wall Street Journal story reported some congressional leaders kept leftover travel money from foreign trips.

Butterfield told the Wall Street Journal he sometimes keeps the extra money. He said that he is going to cooperate with the Office of Congressional Ethics’ probe.

Butterfield said in a statement that the Office of Congressional Ethics contacted him seeking information related to per diem used on a congressional delegation trip. He said that he informed the Office of Congressional Ethics that the funds were spent on legitimate travel expenses, and that if any funds went unspent, they were nominal.

“I also informed (the Office of Congressional Ethics) that I had received a per diem on the trip but did not maintain detailed records because it is not required,” Butterfield said. “While State Department guidelines do not require detailed accounting, (the Office of Congressional Ethics) apparently does not share that opinion and has forwarded the matter to the Ethics Committee. I have complied with the requests of (the Office of Congressional Ethics) and will comply with any other request from the Ethics Committee.”

Other members of Congress under investigation are former U.S. Rep. Mark Souder, R-Ind.; U.S. Rep. Solomon Ortiz, D-Texas; U.S. Rep. Joe Wilson R-S.C.; U.S. Rep. Robert Aderholt, R-Ala.; and U.S. Rep. Alcee Hastings, D-Fla.

Butterfield’s opponent Republican Ashley Woolard has condemned Butterfield’s actions, saying that he was disappointed to learn about the recent report. Woolard said that Butterfield should resign from his post because of the investigation.

The three-term Wilson Democrat will defend his 1st District seat against the Washington, N.C., businessman in the mid-term elections.

Last month, Woolard challenged Butterfield to return $4,000 in donations to U.S. Rep. Charlie Rangel, D-N.Y. Butterfield, who serves on the U.S. House ethics committee, received the donation from Rangel’s political action committee in 2004 during his first stint at Congress.

Rangel now faces ethics committee charges. Woolard has said that Butterfield’s impartiality could be hindered because he refuses to return the donations and recuse himself from the House ethics panel.

“Citizens of the First District need honest leadership that will help our struggling economy, not another greedy politician feeding at the public trough as our economy burns,” Woolard said in a statement.