Republican House and Senate investigators on Wednesday launched their effort to secure evidence from federal agencies about an Obama-era Russian corruption case as lawmakers prepare to interview a former undercover informant who helped the FBI chronicle bribery, kickbacks and money laundering inside Moscow's nuclear industry.

In letters to the FBI, Justice Department, Treasury Department and intelligence agencies, the congressional investigators demanded to know whether the evidence the FBI gathered starting in 2009 against figures inside Rosatom was circulated to government agencies before the Obama administration made a series of favorable decisions between 2010 and 2012 benefitting the Russian nuclear firm.

One of those decisions included the Committee on Foreign Investment in the United States (CFIUS) approval of a sale of the Uranium One firm with large U.S. assets to Rosatom, while others opened the door for Rosatom's Tenex arm to win lucrative commercial nuclear fuel contracts.

The favorable decisions occurred even as the FBI captured widespread evidence that Tenex official Vadim Mikerin and others were carrying out a racketeering scheme. Three individuals, including Mikerin, eventually pleaded guilty to various crimes.

ADVERTISEMENT "It is unclear to the Committees whether the FBI alerted the other members of the CFIUS about the investigation into Russia's effort to obtain control of the U.S. uranium market," a letter from the House Intelligence and House Oversight and Government Reform Committees read.

"In light of the fact that the confidential informant is now cleared to speak with Congress, please preserve all records relating to his involvement with the Department as an informant and the resulting criminal cases," Grassley wrote.