WASHINGTON, April 27 (Reuters) - The Pentagon's inspector general has launched an investigation into whether Michael Flynn, President Donald Trump's former national security adviser, took money from foreign entities without needed approval, according to a letter released by House Democrats on Thursday.
The inspector general is probing whether Flynn had "failed to obtain required approval prior to receiving any emolument from a foreign government," according to the April 11 letter to the House Oversight and Government Reform Committee.
Flynn is under scrutiny over his contacts with Russian officials, and lawmakers have said he likely broke the law by failing to request and receive permission to accept payments for a 2015 trip to Russia.
RELATED: A look at retired Army Lt. Gen. Michael Flynn
Retired Army Lt. Gen. Michael Flynn
Retired Army Lt. Gen. Michael Flynn
National security adviser General Michael Flynn delivers a statement daily briefing at the White House in Washington U.S., February 1, 2017. REUTERS/Carlos Barria
Retired Lt. Gen. Michael Flynn arrives at the Trump Tower for meetings with US President-elect Donald Trump, in New York on November 17, 2016.
(EDUARDO MUNOZ ALVAREZ/AFP/Getty Images)
Retired United States Army lieutenant general Michael T. Flynn introduces Republican Presidential nominee Donald J. Trump before he delivered a speech at The Union League of Philadelphia on September 7, 2016 in Philadelphia, Pennsylvania. Trump spoke about his plans to build up the military if elected. Recent national polls show the presidential race is tightening with two months until the election.
(Photo by Mark Makela/Getty Images)
Retired Lt. Gen. Michael Flynn, at podium, and Republican presidential candidate Donald Trump attend a campaign event with veterans at the Trump International Hotel on Pennsylvania Ave., NW, where Trump stated he believes President Obama was born in the United States, September 16, 2016.
(Photo By Tom Williams/CQ Roll Call)
WASHINGTON, DC - FEBRUARY 01: White House Press Secretary Sean Spicer (L) yields the briefing room podium to National Security Adviser Michael Flynn February 1, 2017 in Washington, DC. Flynn said the White House is 'officially putting Iran on notice' for a recent missile test and support for Houthi rebels in Yemen. (Photo by Win McNamee/Getty Images)
Army Lt. Gen. Michael Flynn, director of the Defense Intelligence Agency, prepares to testify at a Senate Armed Services Committee hearing in Dirksen Building titled 'Current and Future Worldwide Threats,' featuring testimony by he and James Clapper, Director of National Intelligence.
(Photo By Tom Williams/CQ Roll Call)
White House National Security Advisor Michael Flynn (C) arrives prior to a joint news conference between Canadian Prime Minister Justin Trudeau and U.S. President Donald Trump at the White House in Washington, U.S., February 13, 2017. REUTERS/Carlos Barria
U.S. National Security Advisor Michael Flynn boards Air Force One at West Palm Beach International airport in West Palm Beach, Florida U.S., February 12, 2017. REUTERS/Carlos Barria
National security adviser General Michael Flynn arrives to deliver a statement during the daily briefing at the White House in Washington U.S., February 1, 2017. Picture taken February 1, 2017. REUTERS/Carlos Barria
White House National Security Advisor Michael Flynn (L) arrives at Joint Base Andrews, Maryland, U.S., February 10, 2017. REUTERS/Carlos Barria
WASHINGTON, DC - FEBRUARY 10: (AFP OUT) White House National Security Advisor Michael Flynn (R) walks down the West Wing Colonnade following a bilateral meeting between U.S. President Donald Trump and Japanese Prime Minister Shinzo Abe February 10, 2017 in Washington, DC. Trump and Abe are expected to discuss many issues, including trade and security ties and will hold a joint press confrence later in the day. (Photo by Chip Somodevilla/Getty Images)
ATLANTA, GA - FEBRUARY 02: (L-R) SCAD Dramatic writing professor Chris Auer, Producer Sandra Leviton, Executive producer and writer Michael Flynn, Tv literary agent Jeff Greenberg and Literary manager and producer Kaila York speak on stage during the 'Inside the Writers Room' event on Day One of aTVfest 2017 presented by SCAD on February 2, 2017 in Atlanta, Georgia. (Photo by Vivien Killilea/Getty Images for SCAD)
Lieutenant General Michael Flynn (ret.), National Security Advisor Designate speaks during a conference on the transition of the US Presidency from Barack Obama to Donald Trump at the US Institute Of Peace in Washington DC, January 10, 2017. / AFP / CHRIS KLEPONIS (Photo credit should read CHRIS KLEPONIS/AFP/Getty Images)
Retired Lieutenant General Michael Flynn, U.S. national security advisor, attends a swearing in ceremony of White House senior staff in the East Room of the White House in Washington, D.C., U.S., on Sunday, Jan. 22, 2017. Trump today mocked protesters who gathered for large demonstrations across the U.S. and the world on Saturday to signal discontent with his leadership, but later offered a more conciliatory tone, saying he recognized such marches as a hallmark of our democracy. Photographer: Andrew Harrer/Bloomberg via Getty Images
WASHINGTON, DC - JANUARY 20: Michael Flynn walks out after a morning worship service on Inauguration day at St. John's Episcopal Church in Washington, DC on Friday, Jan. 20, 2017. (Photo by Jabin Botsford/The Washington Post via Getty Images)
WASHINGTON, DC - JANUARY 20: Attorney General nominee Sen. Jeff Sessions (R-AL) (R), talks with National Security Advisor Michael Flynn inside of the inaugural parade reviewing stand in front of the White House on January 20, 2017 in Washington, DC. Donald Trump was sworn in as the nation's 45th president today. (Photo by Mark Wilson/Getty Images)
Retired Lieutenant General Michael Flynn, White House national security adviser-designate, center, stands in an elevator at Trump Tower in New York, U.S., on Thursday, Jan. 12, 2017. Donald Trump is slated to meet with AT&T Inc.'s top executives on Thursday to discuss the company's proposed $85.4 billion bid for Time Warner Inc., according to people familiar with the matter. The president-elect has said he opposes the deal. Photographer: John Taggart/Bloomberg via Getty Images
WASHINGTON, DC - JANUARY 20: Donald Trump's National Security Adviser Gen. Michael T. Flynn (R) arrives on the West Front of the U.S. Capitol on January 20, 2017 in Washington, DC. In today's inauguration ceremony Donald J. Trump becomes the 45th president of the United States. (Photo by Drew Angerer/Getty Images)
Lieutenant General Michael Flynn (ret.) and National Security Advisor Designate and Ambassador Susan Rice, National Security Advisor during a ceremonial passing of authority while participating in a conference on the transition of the US Presidency from Barack Obama to Donald Trump at the US Institute Of Peace in Washington DC, January 10, 2017. / AFP / CHRIS KLEPONIS (Photo credit should read CHRIS KLEPONIS/AFP/Getty Images)
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Representative Elijah Cummings, the top Democrat on the House Committee on Oversight and Government Reform, also released documents from the Pentagon that showed it had found no evidence that Flynn sought permission to receive foreign funds despite being warned in 2014 against taking such payments.
An attorney for Flynn did not immediately respond to a request for comment.
In a redacted version of a letter sent to the committee this week, the Defense Intelligence Agency (DIA) told lawmakers it had found no evidence that Flynn sought approval of or reported any foreign payments.
"DIA did not locate any records referring or relating to LTG (Lieutenant General) Flynn's receipt of money from a foreign source ... DIA did not locate any records of LTG Flynn seeking permission or approval for the receipt of money from a foreign source," the agency wrote April 7.
Cummings also released an October 2014 letter from DIA to Flynn outlining ethics restrictions that applied to him on retirement from the U.S. Army, including a prohibition on accepting payments from foreign sources without permission.
The latest release of documents comes amid congressional investigations of possible ties between Trump's election campaign and Russia.
Flynn resigned on Feb. 13 after failing to disclose his talks with Sergei Kislyak, Russian ambassador to the United States, before Trump took office.