DENVER, Colo. -- What was initially suspected as vandalism that forced the evacuation of a Denver union headquarters turned out to be a wall thermometer that fell and shattered on the floor.

The Denver bomb squad and firefighters were dispatched to assess and cleanup the spilled mercury, said Denver police spokesman Detective John White.

The Service Employees International Union building at 2525 W. Alameda Ave. was evacuated as a precaution just after 10 a.m., White said. The few employees in the building during the holidays were evacuated as a precaution.

Once the mercury was cleaned up and police were allowed to enter the building, they soon realized that it was just an accident -- not the vandalism that employees initially reported, White said.

Investigators were still gathering details on the incident, White said. No suspects were in custody.

Fire Lt. Phil Champagne said it was a relatively small amount of mercury.