Star-Ledger fileConstruction workers enter the Middlesex Water Company plant in Edison in a file photo.

WOODBRIDGE — Residents in parts of Woodbridge and Edison are being told to boil their water because of a water main break on Route 35, and about 50 homes in South Brunswick are without water because of a separate water main break there.

About 4 a.m., a water main 16 inches in diameter broke on Route 35, just south of Route 1, in Woodbridge, the Middlesex Water Co. announced.

The break occurred near the entrance of Woodbridge High School, and students got a day off when the school cancelled classes.

However, the main township library and the health department offices nearby remain open.

Police have been directing traffic through one side of Route 35 to get around the repair work, which is expected to continue through the afternoon and possibly into the early evening, township officials said.

Middlesex Water issued an advisory for people in the Fords, Avenel and Woodbridge proper section of Woodbridge, and the Clara Barton section of Edison.

Residents and businesses are advised to boil water used for eating, cooking, drinking, mixing drinks, making ice cubes, washing dishes or giving to pets. The advisory is in effect through Thursday.

Water pressure has also dropped in the system, but is expected to increase this afternoon, Woodbridge officials said.

In South Brunswick, a water main broke on Riva Avenue near Ireland Brook today, and water service was cut off in the area, police said. They said water was shut off to about 50 homes in the area, and there was no immediate estimate when service would resume.