The close relationship between Scott Pruitt, the new administrator of the Environmental Protection Agency, and fossil fuel interests including the billionaire Koch brothers has been highlighted in more than 7,500 emails and other records released by the Oklahoma attorney general’s office on Wednesday.

The documents show that Pruitt, while Oklahoma attorney general, acted in close concert with oil and gas companies to challenge environmental regulations, even putting his letterhead to a complaint filed by one firm, Devon Energy. This practice was first revealed in 2014, but it now appears that it occurred more than once.