The city says about 50,000 gallons of sewage spilled into the Los Cerritos Channel Saturday when a pump station lost power.
The city's health department is monitoring the water quality. This will continue until results meet state standards.
More samples will be taken Monday. Depending on the results, some beaches may reopen and some may remain closed.
Long Beach oversees about seven miles of public beaches. Water samples are typically collected weekly to monitor bacteria levels.