A half-mile section of San Francisco's Ocean Beach was closed Wednesday as crews worked to clean up a large sewage discharge.

Crews saw the discharge coming from a manhole near Great Highway and Balboa Street at about 1 a.m., San Francisco Public Utilities Commission spokeswoman Jean Walsh said.

SFPUC and Department of Public Works crews were at the scene doing cleanup all day Wednesday.

Walsh said 90 percent of the discharge was rainwater, and that there were been no reports of a foul odor.

Officials said that during the overnight rain storm, the sewer system became overloaded and water burst through a manhole cover at the intersection of the Great Highway and Balboa St.

The discharge was on the sand and on its “pedestrian promenade,” and that the spill spanned about a block, according to Walsh. SFPUC crews estimated that the spill was 90 percent rainwater and 10 percent sewage.

Crews used a bleach mixture to disinfect the promenade before reopening it.

Officials said that the beach was expected be closed for up to a week.

"We're sectioning it off just so people don't come in contact with it, play around in it or have their dogs in it. and then we're going to do the water quality testing which we do after any event to make sure the bacteria levels are low enough to reopen it,” said SFPUC spokesman Tyrone Jue.

The SFPUC was also taking data from a sensor on the manhole and investigating the pressure level and what caused the backup.

Crews posted signs warning residents, tourists and surfers.

Some people said they were concerned about the contamination.

“Because it's pollution and you can get sick from it. And it does, as you see there's nobody in the water,” said Jeff Mayhew, a San Francisco resident.