Two Republicans on the Federal Trade Commission asked the White House on Tuesday to disclose any “mounting evidence” of wrongdoing behind high retail gasoline prices after President Joe Biden urged the agency to dig deeper into possible “illegal conduct” in the market.

FTC Commissioners Noah Phillips and Christine Wilson asked the administration to share the evidence “so that we might consider how to proceed.”

Last week, Biden told FTC Chair Lina Khan there was “mounting evidence of anti-consumer behavior by oil and gas companies” and he urged the commission to “further examine what is happening with oil and gas markets.”

“I do not accept hard-working Americans paying more for gas because of anti-competitive or otherwise potentially illegal conduct,” Biden said in a letter to Khan.

The White House said in a statement that the price at the pump normally moves with the price of wholesale gasoline.

“But recently there has been a split where the price of refined gas is going down but prices at the pump are going up. The split is now nearly 30 cents larger than its historical average,” a White House official said.

The two Republican commissioners said they shared the concern of all Americans about current gasoline prices, but noted the FTC had been asked to probe gasoline prices during previous administrations and found no evidence of collusion or other illegal behavior.

“The FTC has a long history of studying the oil and gas industries,” they wrote. “For example, our agency’s work has highlighted the fact that prices at the pump may not correlate immediately with the price of crude.”

Crude oil prices recently touched seven-year highs and although they are still some way short of levels reached between 2011 and 2014, when they broke through $100 a barrel, many consumers are feeling the pain of a dramatic increase from a year ago.

The United States said on Tuesday it would release millions of barrels of oil from strategic reserves in coordination with China, India, South Korea, Japan and Britain, to try to cool prices after OPEC+ producers repeatedly ignored calls for more crude.

Biden said the move would help lower gasoline prices.

“I told you before that we’re going to take action on these problems. That’s exactly what we’re doing,” Biden said in remarks broadcast from the White House.

“It will take time, but before long you should see the price of gas drop where you fill up your tank,” he said.