FLINT, Mich. (AP) — An entire Michigan city has been placed on a boil water advisory after crews discovered a massive water main break.

The advisory in Flint was announced late Friday morning by the mayor’s office.

The break occurred in a 24-inch transmission line, according to WJRT-TV.

Water officials said it could cause a drop in water pressure for homes and businesses throughout the city.

Customers are advised to boil water before using it for drinking, cooking, brushing teeth or washing dishes. The advisory could remain in place until Monday.

Flint has about 80,000 residents and is 68 miles (109 kilometers) northwest of Detroit.

In 2014, Flint’s water became tainted with lead after officials started using the Flint River to save money while a new pipeline to Lake Huron was built. The water wasn’t treated to reduce its corrosive qualities, causing lead to break off from old pipes and contaminate the system for more than a year.