The 52-story Prudential Center in Boston was evacuated Friday because of a burst pipe.
A spokesman for the city's Water and Sewer Department, Tom Bagley, says a water pipe burst within a cooling tower Friday morning, causing water damage and a power outage that disabled the building's elevators.
Bagley says workers are walking down many flights of stairs without air conditioning. No injuries are reported and witnesses describe the evacuation as calm and orderly.
About 2,000 people work in the tower on a typical weekday.
Fire officials and a spokeswoman for the Prudential Center did not immediately return calls for comment.