CVR Energy  (CVI - Get Report) shares were down 1.5% to $21.96 in afternoon trading Tuesday shortly after a letter sent by eight Democratic Senators requested an Securities and Exchange probe into majority stake holder Carl Icahn. 

CVR Energy had spent most of the day in positive territory before the development. 

"We are writing to request that your agencies investigate whether Carl Icahn violated insider trading laws, anti-market manipulation laws, or any other relevant laws based on his recent actions in the market for renewable fuel credits," the Senators said in a letter to the heads of the Securities and Exchange Commission Tuesday.

Icahn proposed changes to the U.S. biofuels program that would ease the regulatory burdens of biofuel companies in February, shortly after he was named an adviser to Trump's administration following his election in November.

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