(CNN) EPA Administrator Scott Pruitt's 24-hour security in Washington extends to at least some of his personal trips, according to a letter Democratic Sen. Sheldon Whitehouse sent to the department's inspector general and shared with CNN.

The letter, written based on information that Whitehouse says he confidentially obtained from an unnamed source, raises new questions about the cost of Pruitt's unprecedented EPA-funded security, and alleges that Pruitt has used his security detail while on non-official business, including trips home to Tulsa, Oklahoma, a family vacation to Disneyland and the Rose Bowl game.

Whitehouse, D-Rhode Island, says the new details should be added to the inspector general's ongoing investigation into Pruitt's travel expenses and use of a 24/7 security detail. The documents, he wrote, raise concern "significant agency resources are being devoted to administrator Pruitt's 'round-the-clock security, even when he is traveling on non-official business."

Whitehouse adds, "While I consider matters of personal security to be extremely serious, personal security should never be used as a pretext to obtain special treatment."

PASADENA, CA - JANUARY 01: Baker Mayfield #6 of the Oklahoma Sooners scrambles in the 2018 College Football Playoff Semifinal Game against the Georgia Bulldogs at the Rose Bowl Game presented by Northwestern Mutual at the Rose Bowl on January 1, 2018 in Pasadena, California. (Photo by Harry How/Getty Images)

The letter alleges that six weekly schedules and other explanatory documents that were provided to him show that Pruitt used between two and three dozen different agents during a six-week period.

Read More