DALY CITY (KRON)—An estimated 400 students were told to stay home from school Tuesday morning because of a plumbing problem at Westlake Elementary in Daly City.

The district superintendent says the school had a clogged sewage line last week that they thought they’d cleared, but the blockage turned out to have just moved on.

On Tuesday morning, a maintenance crew discovered backed up drains in two student bathrooms and boiler room.

“Our students were not able to use their bathrooms and flush,” said school superintendent Bernie Vidales. “And so we’re not able to get portable bathrooms in time for start of school and so for the safety and comfort students and staff we determined we would cancel school for the day.”

The clog was cleared later in the day and the city flushed their mains as well to make sure it wasn’t a problem on their end.

School will be back open Wednesday morning.