A Janesville Gazette report says officials responded Sunday about 1 p.m. to a report of water shooting out from the pipe.
The water reached higher than a nearby three-story building. The street had a gaping 10-foot-wide hole that was growing as the deluge continued. Water and rubble poured down a hill, and police blocked off streets as crews worked to shut down the main.
City water crew spokesman Randy Westby says it's not clear whether the break was related to ongoing problems with freezing pipes and deep frost in the ground. He said the water would have to be shut down before the cause could be investigated.