A coalition of Democratic senators is asking the Commodities Futures Trading Commission, Securities and Exchange Commission, and Environmental Protection Agency to investigate Carl Icahn—a top adviser to President Trump and majority owner of a petroleum refining company—for potential insider trading and market manipulation related to the market for renewable fuel credits.

As the majority owner of CVR Energy, Icahn bet heavily in 2016 on a drop in the price of renewable fuel credits, which ultimately resulted in a $50 million windfall for the company, a May 9 letter to the heads of those agencies alleges. He then secured a position as a senior adviser to President Trump, from which he was able to influence decisions that drove down the price of the credits.

Beginning in late 2016, a series of events occurred which eventually reduced the price of renewable fuel credits by roughly 70 percent from peak cost, the letter says. President Trump, reportedly acting on advice from Icahn, selected Scott Pruitt, a vocal critic of the renewable fuel program, as his choice for EPA Administrator.

Public reports in February 2017 then indicated that Icahn, in his role as a special advisor, proposed to the White House a number of changes to the renewable fuel credit program that drove down prices—all while his company was allegedly dumping credits to buy back later at a cheaper price.

“We have no way of knowing at this time whether Mr. Icahn made any of his renewable fuel credit trades or decisions about trades based on material, non-public information or otherwise manipulated the market,” the senators wrote. "But the publicly available evidence is troubling, and based on this evidence, we ask that your agencies investigate whether Mr. Icahn's conduct violated any laws under your jurisdiction."

The senators raised their concerns with the CFTC, SEC and EPA because these agencies maintain jurisdiction over insider trading and market manipulation of renewable fuel credits and other securities and commodities laws.

In the letter, they asked the three agency heads to assess the "precise nature and extent of Mr. Icahn's communications with President Trump and other administration officials during and after the presidential transition," as well as "the extent to which Icahn influenced the administration's decisions that affected the market for renewable fuel credits and associated markets."

The senators also asked for an analysis of Icahn's decision making process in relation to the selling and purchase of credits, and whether he had access to any material, non-public information or provided such information to the media or the public.

Senators signing the letter included Elizabeth Warren (D-Mass.), Debbie Stabenow (D-Mich.), Tom Carper (D-Del.), Sherrod Brown (D-Ohio), Sheldon Whitehouse (D-R.I.), Tammy Baldwin (D-Wis.), Tammy Duckworth (D-Ill.), and Amy Klobuchar (D-Minn.),