SAN FRANCISCO -- Temporary repairs to a damaged section of roadway in San Francisco's South of Market neighborhood were completed overnight, following a water main break Saturday that caused a massive 20-foot-wide sinkhole.

The sinkhole opened Saturday night after a water main ruptured at 10th and Division streets at about 8:30 p.m. The area is near a five-street intersection underneath the city's Central Freeway.

No injuries were reported, but westbound Brannan Street between Ninth and 10th streets had to be closed for repairs.

Crews poured concrete over the 8-foot-deep hole on Monday and later put a temporary patch on top of the concrete, allowing the roadway to be reopened by midnight Monday, San Francisco Public Utilities Commission spokesman Tyrone Jue said.

A permanent top layer of asphalt will be added at a later date, he said.

The 16-inch pipe that broke Saturday was a major water transmission line serving the South of Market area, the Mission District, downtown San Francisco and Chinatown, Jue said.

Crews were able to reroute water service after the rupture to prevent water loss to those neighborhoods, Jue said. The handful of residents and business that did lose water service saw it restored by about 3:30 p.m. Sunday.

Along with the SFPUC, crews from Caltrans, Pacific Gas and Electric Co. and the Department of Public Works responded to inspect the damage.

"Anytime you have a significant break in a water main, it usually does result in a sinkhole, because it washes out the dirt beneath the roadway," Jue said.

"It definitely was a significant sinkhole," he said.

The cause of the break has been attributed to the age of the 100-year-old pipe and the cold weather.

Jue said San Francisco averages about 100 water main breaks each year, "which is very good considering the age of our system," he said. "San Francisco is a pretty old city."