House Democrats are asking for new documents on former national security adviser Michael Flynn, who has become a central figure in the congressional Russia investigation, related to any connection he has with Saudi Arabia and his apparent “failure to accurately report … foreign travel and contacts."

Reps. Elijah Cummings, the top Democrat on the House Oversight Committee, and Eliot Engel, the lead Democrat on the Foreign Affairs Committee, on Monday requested information related to Flynn’s travel before he joined the administration. In particular, the letter highlights a trip Flynn reportedly took to the Middle East “in the summer of 2015 to pursue a joint US-Russia business venture to develop nuclear facilities located in — and financed by — Saudi Arabia.”

The Democrats sent the letter to Flynn’s lawyer and two companies involved in the deal, one of which Flynn advised. The letter points to a Newsweek report from earlier this month, which said that Flynn made the trip to Cairo and Jerusalem on behalf of the firm he advised, X-Co Dynamics Inc./IronBridge Group, to “gauge attitudes” toward the Saudi-financed US–Russian project that would provide nuclear power in the Middle East.

The Democrats write that they “have no record” that Flynn disclosed the trip when he applied for a new security clearance to join the Trump administration in January 2016. The letter goes on to quote the security clearance application, which states that “knowingly falsifying or concealing a material fact” on the form could lead to fines and/or five years in prison.

The two Democrats are requesting, by the end of the month, documents and communication related to Flynn’s travel, and information on his — or the Flynn Intel Group’s — relationship with X-Co Dynamics Inc./IronBridge Group and ACU Strategic Partners. According to Newsweek, ACU Strategic Partners was “one of the lead companies involved” in the power project.

(Flynn and the Flynn Intel Group have been subpoenaed by the House Intelligence Committee in relation to its Russia investigation.)

The letter also raises questions about the details of another trip Flynn made in 2015, to Saudi Arabia. The Democrats note that Flynn did disclose that trip, but argue that he “omitted significant details.” The Democrats are requesting information about the trip — including who sponsored it, the identity of the “friend” Flynn reported that traveled with him, which conference he attended while in the country, and where he stayed.

The two Democrats wrote that they’re looking into “what influence General Flynn’s business interests with Saudi Arabia, Russia, or other countries may have had after he assumed his post in the White House.” They go on to note that Saudi Arabia was the first foreign country that Trump visited as president, and that the Trump administration recently “concluded” an arms deal with the country, questioning “what advice or input General Flynn may have offered relating to these matters, if any.”

“Most troubling of all, we have no record of General Flynn identifying on his security clearance renewal application— or during his interview with security clearance investigators— even a single foreign government official he had contact with in the seven years prior to submitting his security clearance application,” the pair wrote.

Flynn was fired only 24 days into the Trump presidency after he was accused of misleading Vice President Mike Pence about Flynn's communication with the Russian ambassador to the US during the transition.

This is not the first time House Democrats have requested additional documents on Flynn. Cummings and other Democrats on the Oversight Committee have previously released information showing that the Defense Department’s inspector general was investigating Flynn over payments Flynn received from Russia-linked entities, including RT, after he retired from the Defense Intelligence Agency.