A house committee is investigating former National Security Adviser Michael Flynn over potentially illegal funds he might have received.

Meanwhile, some officials are saying that he may not face any criminal charges.

Law enforcement sources told CBS News they believe there is not enough evidence to charge him with a crime.

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A house committee is investigating former National Security Adviser Michael Flynn, left, over potentially illegal funds he might have received. The House Oversight and Government Reform committee hopes to learn whether Flynn received payouts from the Russian government

Law enforcement sources believe there is not enough evidence to charge him with a crime after he was investigated for a call with a Russian official in which he discussed sanctions, lied about discussing sanctions and told Mike Pence, who proceeded to tell the public, the lie

Flynn might have violated federal law when he discussed Obama's sanctions on Russia with Sergey Kislyak, Russia's ambassador to the United States, before Trump's inauguration.

He was later investigated for this call by the FBI and told VP Mike Pence - who proceeded to tell the public - that he did not discuss sanctions.

A transcript of the call shows otherwise, sources said.

The investigation from the House Oversight and Government Reform committee specifically pertains to how much Flynn was paid - and who paid him - for a trip to Moscow in December 2015, Yahoo reported.

A bipartisan letter from Republican representative Jason Chaffetz, of Utah, and Democratic representative Elijah Cummings, of Maryland, is asking Leading Authorities, Flynn's speakers bureau, to reveal how much Flynn was paid when he attended a December 2015 celebration of the 10th anniversary of Russia Today.

Flynn might have violated federal law when he discussed Obama's sanctions on Russia with Sergey Kislyak, Russia's ambassador to the United States, before Trump inauguration

On the same trip, he also sat for a 44-minute interview with Russia Today.

The media organization has been criticized for allegedly serving as a mouthpiece for the Russian government and for covertly helping to undermine the presidential candidacy of Democrat Hillary Clinton.

The committee hopes to learn whether Flynn received payouts from the Russian government, which may have violated Department of Defense guidelines.

The guidelines prohibit even retired military officers from receiving gifts from foreign governments.

Flynn had retired from his role as the director of the Defense Intelligence Agency in August 2014 - though sources including Colin Powell said he was, in fact, fired, the Washington Post reported.

Chaffetz and Cummings wrote a letter to the president of Leading Authorities, in which they said they are trying to determine 'whether Flynn may have received payments from any foreign governments for additional engagements.'