Long Beach health officials closed all swimming areas west of Belmont Pier after 26,241 gallons of sewage from the city of Los Angeles spilled into the Los Angeles River on Monday.

The spill was caused by construction work on a 48-inch sewer main line, the city said in a statement Monday evening, citing a report from the governor’s office of emergency services earlier in the day.

The city will monitor water quality in the area of the spill over the next few days and test for bacterial levels. Until they met state standards, the swimming areas will remain closed, officials said.