On May 9, a group of senators issued a letter to the heads of the U.S. Commodities Futures Trading Commission, the Securities and Exchange Commission and the U.S. EPA calling for an investigation of Carl Icahn for potential insider trading, market manipulation and other securities and commodities law violations related to the market for renewable identification numbers (RINs), which are used by obligated parties to comply with Renewable Fuel Standard regulations.

Icahn is the majority owner of CVR Energy, which is a petroleum refining company involved in the RIN market. In late December, he was also named as a special advisor to President Donald Trump on issues related to regulatory reform.

In the letter, the senators said that “Icahn ‘made a massive bet in 2016’ that the price of renewable fuel credits would drop,” and noted that he, as an unpaid advisor to Trump, recommended personnel and policies that caused the price of these RIN credits to drop. “The net result was an ‘impossible’ ‘rare profit’ on the credits, ‘a $50 million turnaround’” from Icahn’s initial investment, continued the senators in the letter. According to the senators, these actions and profits raise questions over whether Icahn may have violated conflict-of-interest rules that apply to government officials.

The senators state that CRV Energy delayed purchases of necessary RINs over the course of 2016, including in the months immediately preceding and following the election, and instead sold millions of them. The action is described as a counterintuitive trading strategy and a bet that the company could buy needed RINs later at lower prices.

The letter cites reports that Icahn advised Trump to nominate Scott Pruitt, a critic of the RFS program, to serve as administrator of the EPA. The letter notes that RIN prices dropped by nearly 20 percent following Pruitt’s nomination. In addition, the senators note that press reports in late February indicating Icahn had presented the White House with executive language to modify the RFS, RIN prices dropped again, reaching a 17 month low. The letter credits these actions with contributing to a 70 percent decline in RIN prices when compared to the November peak cost of the credits.

“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,” said the senators in the letter. “But the publically 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.” In addition to requesting five specific areas of investigation, the letter also asks that Pruitt and SEC Chairman Jay Clayton recuse themselves from the matter due to potential conflicts of interest.

The letter is signed by Sens. 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. A full copy of the letter is available on Warren’s website.