"Documents provided to us by EPA official (s) suggest the agency has relied on questionable threats to the Administrator, including reports of non-violent protests, negative feedback about the administrators actions or other First Amendment protected activity to justify millions of dollars in additional security spending, inducing first-class air travel, as compared to his predecessors at the agency", Carper and Whitehouse wrote.
Sen. John Barasso, R-Wyo., said Tuesday he would not hold a hearing on the issue.
EPA's Intelligence Team asked the United States Secret Service to provide a "Direction of Interest Query" in February 2017 and again this February on potential threats against Pruitt, the senators write, and neither query returned any "reports of behaviors of interest directed toward EPA Administrator Pruitt".
The EPA pushed back against the criticisms. Duckworth's office has not responded to CNN's request for comment.
"Any reasonable reading of these documents supports the Office of the Inspector General's statements that Administrator Pruitt faces a 'variety of direct death threats, '" he said. We are watching you.
Ryan Jackson, chief of staff at the EPA, is taking responsibility for the controversy surrounding pay increases given to two aides of Administrator Scott Pruitt. "EPA Intelligence has not identified any specific credible direct threat to the EPA Administrator", the lawmaker's letter, obtained by the Times, states.
Politico first reported Tuesday that the career EPA security staffer who wrote the February memo, Mario Caraballo, was sacked shortly after the Democrats' account of it became public. The Associated Press first reported last week that the 20-member team tasked with providing day-and-night protection for Pruitt had racked up salary, overtime and travel expenses approaching $3 million.
The Office of Government Ethics also has issued a letter to EPA demanding documents related to the condo rental.
The Carper-Whitehouse letter cites a memo from William Stull, special agent on Pruitt's private security detail, to Nino Perrotta, the detail's special agent in charge, which summarizes available threat information and shows 16 threats directed against Pruitt.
Trump defended Pruitt in a tweet over the weekend, saying the EPA chief is "doing a great job".
The conservative bid to rally around Pruitt came as three Republican senators criticized him and Senate Democratic Leader Chuck Schumer called for Pruitt to resign or be fired amid expanded ethics investigations of his spending and possible perks he's received. Barrasso said he saw the positive impact of Pruitt's actions late last month as he and Pruitt toured a Wyoming coal mine. In one incident, someone yelled profanity as he walked through the airport. Leopold told AP this week that an EPA official who responded to his request told him verbally that after checks with the agency's general counsel and inspector general's office that no such records existed.