(CNN)The EPA's Office of Inspector General announced Monday it is beginning a "preliminary investigation" into Administrator Scott Pruitt's travel after a hotline complaint and congressional requests which "expressed concerns" about frequent travel to Oklahoma -- his home state -- "at taxpayer expense."

In a press release, the EPA IG says it will begin work this week to determine "the frequency, cost and extent of the administrator's travel that included trips to Oklahoma" through the end of July, whether "applicable EPA travel policies" were followed, and whether EPA policies "are sufficiently designed to prevent fraud, waste and abuse."

In late July, the watchdog group Environmental Integrity Project said travel records from a Freedom of Information Act request show that Pruitt spent 48 of 92 days in March, April and May traveling -- including 43 days on trips that included stops in his home state of Oklahoma.

"We are glad that the EPA Office of Inspector General is looking into this issue to determine whether taxpayer funds were spent appropriately," said Sylvia Lam, an attorney for the Environmental Integrity Project.