Story updated at 12:47 p.m. EDT.

Retired Lt. Gen. Mike Flynn may have lobbied on behalf of a vast foreign deal to build a fleet of nuclear reactors across the Middle East as he was serving as national security adviser, according to new documents out Wednesday.

Two top House Democrats raised the question about Flynn's use of his office in a letter they sent to a pair of business leaders with whom Flynn worked on the project.

"Your responses raise significant questions about whether General Flynn continued to communicate with you and others about this project after the presidential election ... and after General Flynn assumed the post of national security adviser — without disclosing his foreign travel or contacts," they wrote.

The letter is signed by the ranking members of the House Foreign Affairs Committee, Eliot Engel, D-N.Y., and the House Oversight Committee, Elijah Cummings, D-Md. The two Democrats write that they are sharing their findings with Justice Department special counsel Robert Mueller and the Republican chairmen of their committees.

Cummings and Engel have been corresponding with two nuclear energy impresarios who worked with Flynn on behalf of the deal starting in 2015. This involved travel to Egypt and Israel that raises potential problems for Flynn, since he did not report his trips or contacts with foreign officials — which was required after he retired from the Army.

What's new is Engel and Cummings' suggestion that Flynn might have kept up his work with the would-be nuclear-deal brokers from within the White House, and potentially have advocated for them with the State Department, Defense Department or President Trump.

"The American people deserve to know whether General Flynn was secretly promoting the private interests of these businesses while he was a campaign adviser, a transition official or President Trump's national security adviser," the House leaders wrote.

The business partners with whom Flynn worked told the members of Congress they believe the nuclear power plan remains "an ongoing, viable project" that is "now part of the Trump administration's 'toolkit' for the Middle East."

The hugely ambitious scheme involves a consortium — including the United States, Russia, possibly China and companies from many other countries — building a network of 40 nuclear reactors across the Middle East, along with a major new electrical distribution network.

The whole thing would be "fully funded by the Gulf Arab states," according to its backers, and the improvement in stability and security it would yield in the Middle East meant Flynn "firmly believed in the necessity of the project from a U.S. national security perspective," they said.

So Flynn, who ran an advisory and influence business after he was ousted as head of the Defense Intelligence Agency, got on board and traveled in the Middle East to promote the nuclear project — though failed to disclose he was doing so.

A representative for Flynn's business, based outside Washington, D.C., did not deny that Flynn had traveled to the Middle East as part of the plan or had met with foreign contacts and omitted those details from his official reporting. But there was no additional comment in the material released by Engel and Cummings.

Separately, NBC News reported on Wednesday that Flynn's son, Michael Flynn Jr., is a subject in the ongoing federal investigation about Russian interference in the 2016 election. The younger Flynn "had a heavy hand" in the daily operations of Flynn's company, the network reported.

Cummings has previously documented payments from Russian entities to Flynn, which he did not report as required, and earlier questions have also been raised about his advocacy for Turkey.

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