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WASHINGTON — Whistleblowers from within President Donald Trump's National Security Council have told a congressional committee that efforts by former national security adviser Michael Flynn to transfer sensitive nuclear technology to Saudi Arabia may have violated the law, and investigators fear Trump is still considering it, according to a new report obtained by NBC News.

The House Oversight Committee has formally opened an investigation into the matter, releasing an interim staff report that adds new details to previous public accounts of how Flynn sought to push through the nuclear proposal on behalf of a group he had once advised. Tom Barrack, a prominent Trump backer with business ties to the Middle East, also became involved in the project, the report says.

Just days after Trump's inauguration, backers of the project sent documents to Flynn for Trump to approve, including a draft Cabinet memo stating that the president had appointed Barrack as a special representative to implement the plan and directing agencies to support Barrack's efforts, the report says.

Career national security officials objected to the plan, citing what they deemed Flynn's conflict of interest, and also that the proposal sought to bypass a policy review that is required whenever nuclear technology is transferred to another country, the report says.

The proposal, which involved enlisting the U.S. nuclear power industry to build nuclear plants across the Middle East, was backed by a group of retired generals who formed a firm called IP3. Flynn described himself in financial disclosure filings as an "advisor" to a subsidiary of IP3, IronBridge Group Inc., from June 2016 to December 2016 — at the same time he was serving as Trump's national security adviser during the presidential campaign and the presidential transition, the report says.

The report quotes one senior Trump official as saying that the proposal was "not a business plan," but rather "a scheme for these generals to make some money," and added, "OK, you know we cannot do this."

Click here to read the House Oversight Committee report.

"The whistleblowers who came forward have expressed significant concerns about the potential procedural and legal violations connected with rushing through a plan to transfer nuclear technology to Saudi Arabia," the report says.

"They have warned of conflicts of interest among top White House advisers that could implicate federal criminal statutes. They have also warned about a working environment inside the White House marked by chaos, dysfunction, and backbiting."

The Oversight Committee, led by Rep. Elijah Cummings, D-Md., said its investigation of the plan "is particularly critical because the administration's efforts to transfer sensitive U.S. nuclear technology to Saudi Arabia appear to be ongoing."

On Feb. 12, the report notes, Trump met with nuclear power developers at the White House about sharing nuclear technology with countries in the Middle East, including Saudi Arabia. Next week Trump son-in-law and adviser Jared Kushner is set to embark on a tour of Middle Eastern capitals — including Riyadh — to discuss the economic portion of the administration's Middle East peace plan.

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"Experts worry that transferring sensitive U.S. nuclear technology could allow Saudi Arabia to produce nuclear weapons that contribute to the proliferation of nuclear arms throughout an already unstable Middle East," the report says.

Marshall Plan for the Middle East

The proposal, dubbed by its backers a "Middle East Marshall Plan," involved IP3 International, which is short for "International Peace Power & Prosperity." Among those involved with IP3, according to published reports, were Gens. Keith Alexander, Jack Keane and James Cartwright; former Middle East envoy Dennis Ross; George W. Bush homeland security adviser Fran Townsend; and Robert "Bud" McFarlane, who was one of Ronald Reagan's national security advisers. Keane was considered by Trump for secretary of defense.

The House oversight report says whistleblowers told the committee that one of Flynn's top aides, Derek Harvey — who was the senior director for Middle East and North African Affairs at the National Security Council from January to July 2017 — stated during the first week of the Trump administration that Flynn had already decided to adopt IP3's nuclear plan and develop "dozens of nuclear power plants."

Seven days after the inauguration — and two days before a scheduled call with King Salman of Saudi Arabia — Harvey met in his office at the White House with a group of retired generals who work for IP3, including its co-founders, Keane and McFarlane, the report says.

Immediately after the meeting, Harvey directed the NSC staff to add information about IP3's "plan for 40 nuclear power plants" to the briefing package for Trump's call with King Salman.

The report says career staff warned that any transfer of nuclear technology must comply with the Atomic Energy Act, and that the United States and Saudi Arabia would need to reach what is known as a "123 Agreement," which would lay out how Saudi Arabia should comply with nonproliferation requirements.

"Harvey reportedly ignored these warnings and insisted that the decision to transfer nuclear technology to Saudi Arabia had already been made," the report says.

Both career and political staff inside the White House agreed that Harvey's directive could violate the law, the report says.

According to whistleblowers, the National Security Council's ethics lawyer determined that Flynn's involvement could violate the criminal conflict of interest statute, the report says. As a result, NSC legal adviser John Eisenberg instructed NSC staff to cease all work on the plan.

But Harvey continued to pursue the matter, the report says, even after Flynn had been fired in February 2017 for lying to the FBI.

Harvey stated during a meeting on March 2, 2017: "I speak with Michael Flynn every night," the report says.

In mid-March 2017, deputy national security adviser K.T. McFarland reportedly stated during a meeting that Trump told Barrack that he could lead the implementation of the plan, the report says.

Harvey subsequently held a conference call with Barrack and Rick Gates, Trump's former deputy campaign manager and deputy chairman of the Inaugural Committee, who has pleaded guilty to crimes and is cooperating with special counsel Robert Mueller.

At the time, Gates had been hired by Barrack to manage the Washington office of Barrack's company. A career NSC staffer who joined the call later told colleagues that Harvey was trying to promote the IP3 plan "so that Jared Kushner can present it to the president for approval," the report says.

Flynn's replacement, H.R. McMaster, ultimately ordered the council to cease all work on the matter, the report says. He fired Harvey, who is now a minority staffer for the House Intelligence Committee.

Inaugural Committee chairman Tom Barrack speaks at at a pre-Inaugural "Make America Great Again! Welcome Celebration" at the Lincoln Memorial in Washington on Jan. 19, 2017. David J. Phillip / AP file

The report raises further questions about Flynn, who is awaiting sentencing as he cooperates with Mueller. It says Flynn failed to report in his security clearance renewal application a trip he took to Saudi Arabia in June 2015 on behalf of IP3 and its predecessor company. Although he reported a separate trip to Saudi Arabia in October 2015, Flynn omitted key details, the report says, including the identity of the client that financed the trip.

Flynn claimed he spoke at a conference during the trip, but none of his three speakers' bureaus had any involvement with the trip or knew of any conference there, the report says. Flynn told investigators that he stayed at the King Khaled International Hotel, but a U.S. consulate official could not identify any such hotel in Saudi Arabia, the report says.

Both Republicans and Democrats in Congress have expressed concerns about transferring nuclear technology to Saudi Arabia, the report notes.

In October, Republican Senators Marco Rubio, Todd Young, Cory Gardner, Rand Paul, and Dean Heller sent a letter to Trump urging him to "suspend talks related to a potential civil nuclear cooperation agreement between the United States and Saudi Arabia" due to "serious concerns about the transparency, accountability, and judgment of current decisionmakers in Saudi Arabia."

They said they were concerned that "the Saudi Government has refused, for many years, to consider any agreement that includes so-called 'Gold Standard' requirements against pursuing technologies to enrich uranium and reprocess plutonium-laden spent nuclear fuel."

The House Oversight Committee is sending requests for additional documents to the White House and the Departments of Commerce, Defense, Energy, State, and Treasury, the Joint Chiefs of Staff, the CIA, and companies involved with this effort, including IP3, the Flynn Intel Group, ACU Strategies, and Colony NorthStar, the report says.

The committee is also seeking interviews with the key people involved with promoting this plan to the White House.

The White House, Harvey and an attorney for Flynn did not immediately respond to NBC News requests for comment.