Washington (CNN) Seven former Environmental Protection Agency administrators have offered lawmakers help to investigate the department, saying "much is at stake" as the Trump administration seeks to roll back clean air and water regulations, among other policy changes.

The former administrators who signed the letter served under both Democratic and Republican presidents, including Carol Browner, who served under Bill Clinton, Lee Thomas who served under Reagan and Christine Todd Whitman, who served under George W. Bush.

The letter was first reported by E&E News

"We are united that there has never been a more important time for us to put aside our differences and advocate collectively for public health and the environment. Time is of the essence and much is at stake," the letter states.

"As you go about creating an oversight strategy and a path forward, we would like to convey our personal willingness to connect you with resources on substance and sounding boards on priorities," it adds.

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