A Daly City neighborhood woke up Tuesday morning to face floods, mudslides and evacuations.
In all 20 homes were evacuated and at one point, at least 100 people were reported to be without power.
Firefighters told NBC Bay Area that 8-inch cast iron pipe attached to a 978,000-gallon water tank ruptured, causing 45,000 gallons of water to spew out about 4:45 a.m. down Lusanne Avenue in the Hillside Park area. By morning, the park was covered in gooey mud.
The flooding went down Lausanne Avenue and affected a handful blocks coming off that street including Bonnie Street, Clayton Court, East Moltke Street, Ford Street and Price Street.
Raw Video: Daly City Neighborhood Floods
Patrick Sweetland, Daly City's director of public works, said the valve was shut off in about 10 minutes, but it was too late for many cars parked on the street - they were simply deluged by mud.
Clayton Court was one block where residents couldn't move their cars and get to work because their vehicles were stuck in the wet soil and puddles of water.
Emmanuel Romano, who lives nearby, said he had no idea a water tank was housed above his house. "I guess the infrastructure might be getting old," he said.
Sweetland said he didn't know exactly why the pipe burst, but did acknowledge that it's a "pretty old pipe."
An aerial view of the neighborhood showed several cars submerged under a deluge of mud. Crews were busy trying to dig some of those cars out later in the morning.
Clayton Court resident Angel Vega, 83, was in his flip-flops late this morning, shoveling mud out his driveway. He himself was covered in mud.
"I thought it was raining," Vega said of his reaction when the main broke. "It was much worse.
As of 11:30 a.m., all residents had been allowed to return home.
The cause of the water main break has not yet been determined. Engineers were assessing the integrity of the hillside. The initial report showed there was no danger of further mudslides.