The Environmental Protection Agency needs to explain why it didn’t compile years of reports detailing the challenges facing its renewable fuel program and ethanol mandate, said Rep. James Sensenbrenner, a vocal critic of the program.

The Wisconsin Republican, who serves on the House Science, Space and Technology Committee’s oversight panel, sent a letter to EPA Administrator Gina McCarthy Thursday, asking her to detail the reasons why the agency did not fulfill the requirement to conduct the studies and deliver them to Congress.