If his government email record is to be believed, EPA Administrator Scott Pruitt has sent a grand total of one email to anyone outside of the EPA in his first 10 months on the job, causing watchdogs concern as they try to figure out how else he is communicating and if he’s covering his tracks.

According to a Friday Politico report, EPA spokespeople maintain that Pruitt prefers to conduct business in person or over the phone, accounting for the microscopic body of correspondence.

Outside groups counter that it is highly unlikely that someone who meets as frequently with political allies and industry bigwigs as Pruitt would have sent only one email to those external contacts. Some reportedly point out that he also has a history of using private email while serving as Oklahoma’s attorney general and of keeping ethically dubious meetings off the public record.

In addition, his call log is suspiciously empty for the head of a large agency who supposedly conducts the bulk of his business via phone.

Per Politico, the Sierra Club has filed Freedom of Information Act requests and follow-up lawsuits to get records of Pruitt’s correspondence, and is now pushing the EPA to search Pruitt’s private email accounts to ensure that he never used it for government work. If the EPA ignores the request, the Sierra Club could go to a judge to force the review.

Through its efforts, the Sierra Club obtained some text messages, suggesting that much of Pruitt’s contact with outsiders may have been conducted that way. Those records are reportedly much harder to obtain.

Previous reports have catalogued Pruitt’s unscrupulous contact with lobbyists and industry players who have done everything from set up his international trips to try to finagle his wife a job, making the communication void even more suspect.