Military officials explicitly warned Michael Flynn against accepting payments from foreign governments after he left the Pentagon, and instructed him to disclose any such payments if they occurred.

But the retired general subsequently took such a payment and failed to disclose it, according to documents released by congressional investigators on Thursday.

Documents released by the House Oversight Committee show that the Defense Intelligence Agency, which Flynn directed before joining the White House in January, has no record of him disclosing a $33,750 payment from state-sponsored Russian broadcaster Russia Today. Flynn traveled to Moscow in Dec. 2015 to give an address for the network’s tenth anniversary gala. Months later Flynn joined Donald Trump’s presidential campaign as an adviser and was served briefly as National Security Adviser before he was fired in February .

The Republican chairman of the committee, Rep. Jason Chaffetz, asked the Army to issue a final determination on whether Flynn had illegally failed to disclose the RT payment, citing the documents released on Thursday.

"By all appearances, Lt. Gen. Flynn violated [federal law] by accepting compensation from entities associated with foreign governments without obtaining consent to do so,” Chaffetz wrote.

Financial disclosure documents released by the White House early this month showed that Flynn had initially failed to inform federal ethics officials of the payment after taking his White House post.

If he also failed to inform DIA of that payment, Flynn likely ran afoul of federal laws requiring former government officials to seek approval from the State Department and the agencies that once employed them before accepting a payment from a foreign government.

“These documents raise grave questions about why General Flynn concealed the payments he received from foreign sources after he was warned explicitly by the Pentagon,” Rep. Elijah Cummings, the top Democrat on the House Oversight Committee, said in a Thursday statement.

Flynn’s attorney Rob Kelner said this week that Flynn had informed DIA that he would travel to Moscow for the RT event, but would not say whether he had disclosed his payment for speaking at it.

In an emailed statement Kelner disputed Cummings’ characterization of DIA’s letter, saying it was actually exculpatory.

“DIA’s letter actually confirms, in a terse section that is partly redacted, that General Flynn provided information and documents on a thumb drive to the Department of Defense concerning the RT speaking event in Moscow, including documents reflecting that he was using a speakers bureau for the event,” Kelner wrote. “We urge DIA and the Committee to release the full, unredacted letter, along with the documents that General Flynn provided to DIA during the briefings and details concerning the in-person briefings provided by General Flynn to DIA.”

The versions of the documents that were released on Thursday show that DIA has no record of Flynn’s payment from a Russian government-linked entity.

“DIA did not locate any records referring or relating to LTG Flynn’s receipt of money from a foreign source” or “seeking permission or approval for the receipt of money from a foreign source,” the documents state.

Flynn’s foreign payments are currently the subject of an investigation by the Pentagon’s inspector general, according to additional documents released by the oversight committee.

Those documents also show that Flynn was explicitly reminded to seek permission from his former federal employers before seeking or accepting foreign government payments. He “was advised of the legal restrictions concerning foreign compensation and instructed to report any potential receipt of compensation in advance,” according to the DIA letter.

The Emoluments Clause of the Constitution “prohibits receipt of consulting fees, gifts, travel expenses, honoraria, or salary by all retired military personnel, officer and enlisted, regular and reserve, from a foreign government unless congressional consent is first obtained,” DIA told Flynn after his resignation.

The White House has refused to provide the oversight committee with documents relating to Flynn’s brief employment, including a questionnaire in his security clearance application that required him to disclose foreign government payments.

White House press secretary Sean Spicer told reporters on Tuesday that the committee’s request for Flynn’s communications with foreign governments was too voluminous to satisfy. The Pentagon had already provided the questionnaire regarding foreign government payments, he said.

Other documents, Spicer insisted, “the White House can't provide because of its sensitive nature.”

In a press conference announcing the document release on Thursday, Cummings said that the committee has reviewed additional information that raises further concerns about Flynn’s foreign government payments.

That information, Cummings said, “remain under lock and key for now.” He urged the White House “to declassify them so the American public can see them for themselves.”

Democratic members of the oversight committee accused the White House on Thursday of attempting to stonewall their investigation.

“There is obviously a paper trail that the White House does not want our Committee to follow,” they wrote in a joint press release that raised the prospect of “employing compulsory measures” to force the White House’s hand.

Thursday’s revelations sent ripples through the other investigations currently looking into Trump-Russia ties. Some members of the Senate Intelligence Committee, such as Sen. Ron Wyden and Sen. Martin Heinrich, Democrats who have been urging an aggressive inquiry into the Trump orbit, saw the Flynn news as further evidence that they need to be looking at the financial ties between Trump associates and the Russian government.

"Every day that goes by, the more I am convinced at the follow-the-money aspect of this,” Wyden said. “I just can’t begin to count the number of news stories that have highlighted the kind of allegations, the inquiries… with respect to the money trail.”

“There is absolutely no logical or appropriate excuse for [an incomplete SF-86]. It’s a little mind-bongling,” added Heinrich. “The money here is what we need to get to, and I think if we understand some of the financial relationships, we may well understand the nature of what was really going on.”

But Sen. Richard Burr, the chairman of the committee, however, had another view—that the Flynn mess was the responsibility of the Pentagon to investigate, not his panel.

“A majority of Mike Flynn’s problems right now probably are more DoD-related… I’m going to let the Department of Defense handle that,” he told reporters after a classified briefing Thursday afternoon. “We’re going to stay focused on questions and concerns as it relates to Mike Flynn’s contacts with or without consent of a campaign or the White House, and we’ll continue to go down that path, that is jurisdictionally, our responsibility.”

—Tim Mak contributed to this report.