Two employees in the EPA’s Region 8 headquarters in Denver and one who works at the EPA’s National Enforcement Investigations Center in Lakewood are under investigation for signing the letter, said Kate Tribbett, vice president of the American Federation of Government Employees Local 3607, which represents Region 8 employees.

The Environmental Protection Agency has placed roughly 140 employees on administrative leave days after they signed a public letter expressing concern about the treatment of federal employees and the Trump administration’s regulations on climate and public health.