DIXON, Calif. -- A notice to boil water that was issued Tuesday night for some residents of Dixon has been lifted.

The California Water Service Co., a private utility, said a water sample collected on Sunday came back positive for E. coli.

The utility immediately notified the 300 affected households by going door to door after the results came back. The sample was taken from a water main repair site.

"Issuing the boil water advisory following Tuesday's water quality test results was a precautionary measure taken until confirmation water test samples could be verified, and emergency water treatment and additional water quality testing could be completed," local California Water manager Jack Caldwell said in a statement. "Protecting customers' health and safety is our highest priority, and we will continue to monitor the water quality to ensure that it meets all water quality standards."

The Country Faire subdivision and a small portion of the older part of downtown were affected.

Residents are urged to boil water before use until further notice.

The utility did not say if it had determined the source of contamination.