A bipartisan group of House lawmakers say they had no idea that a 2013 congressional trip to Azerbaijan was paid for by that country's government.

At least seven members of Congress or their aides said Wednesday that the lawmakers obtained approval for the May 2013 trip from the House Ethics Committee. Two Houston-based nonprofit corporations reported to the panel that they were sponsoring the conference in the capital city of Baku, near the Caspian Sea.

The Washington Post reported Wednesday that Azerbaijan's state-owned oil company allegedly paid $750,000 to cover travel expenses for the lawmakers — as well as scarves, rugs and other gifts — by sending funds through the nonprofit corporations.

Congressional rules generally bar foreign governments from paying for travel by members of Congress or otherwise trying to influence U.S. policy.

The independent Office of Congressional Ethics and the House Ethics Committee are investigating the trip, which included at least 10 lawmakers from both parties and 32 staffers.

A spokeswoman for Rep. Ted Poe, R-Texas, said Wednesday that the Turquoise Council of Americans and Eurasians told Poe's office and the Ethics Committee before the trip that it was the sole sponsor of the event. The council is one of two companies identified by the Post as entities used by the Azerbaijan government to conceal the fact it paid for the trip. The other company was identified as the Assembly of the Friends of Azerbaijan.

In reality, the State Oil Company of the Azerbaijan Republic allegedly funneled $750,000 through the U.S.-based corporations to pay for the conference in the former Soviet nation, the Post reported.

Poe's spokeswoman, Shaylyn Hynes, said Poe did not learn how the trip was paid for until he was contacted last year by the Houston Chronicle, which published a story in July raising questions about the trip.

"Not only was our office responsive to the Houston Chronicle, we also went a step further by contacting the House Committee on Ethics, self-reporting the allegations raised by the Chronicle to the (ethics) committee and requesting that they look further into them," Hynes said.

Rep. Ruben Hinojosa, D-Texas, said in a statement that he believed the purpose of the trip was to strengthen U.S. relations with Turkey and Azerbaijan, which is rich in oil and natural gas.

"I received souvenirs of what I believed to be of minimal value and in compliance with the House gift rule," Hinojosa said.

Poe, Hinojosa and other lawmakers said they have fully cooperated with the investigation.

Rep. Jim Bridenstine, R-Okla., said in a statement that he made good-faith efforts to follow House rules on gifts. Bridenstine reported on financial disclosure forms that he received two rugs appraised at $2,500 and $3,500, respectively. In a July 2013 letter to the ethics panel, Bridenstine said he wanted to donate the larger, more expensive rug to the House Clerk's Office.

After consulting with the Ethics Committee, he returned the rugs, Bridenstine said.

Others attending the conference were Democratic Reps. Sheila Jackson Lee of Texas; Yvette Clarke and Gregory Meeks of New York; Danny Davis of Illinois and Michelle Lujan Grisham of New Mexico; as well as Rep. Leonard Lance, R-N.J. and former Rep. Steve Stockman, R-Texas.