The nine are reportedly being investigated for inappropriate conduct and damaging the inside of a fire station on the city's north side.
Fire Chief Mark Rohlfing said earlier, that several firefighters have acted "in contravention to our core values." He says his department is consulting with the City Attorney about how to proceed.
According to Michael Tobin, executive director of the Milwaukee Fire and Police Commission, the nine firefighters were suspended Tuesday and are being paid during the investigation.
Rohlfing says the alleged events did not involve citizens.