Federal prosecutors say the FBI is working with a multi-agency team investigating the lead contamination of Flint's drinking water.
U.S. attorney's spokeswoman Gina Balaya in Detroit told The Associated Press in an email Tuesday that her office also is working with the U.S. Postal Inspection Service and U.S. Environmental Protection Agency.
Word of the FBI's involvement was first reported by the Detroit Free Press.
The U.S. attorney's office in Detroit said in January it was investigating the water crisis with the EPA.
Officials haven't said whether criminal or civil charges might follow.
Flint switched its water source from Detroit's water system to the Flint River in 2014 to save money while under state financial management. The river water wasn't treated properly and lead from pipes leached into Flint homes.