BURTCHVILLE TOWNSHIP, Mich. (AP/WOOD) — Authorities posted a boil-water advisory Saturday for more than 900,000 people in southeastern Michigan but then eased it hours later to 13 communities.

The Great Lakes Water Authority reported a break on a critical pipe in St. Clair County, which carries treated water from Lake Huron and is the largest in the system.

“A loss of pressure can lead to bacterial contamination in the water system. … Boiling water before using it will kill bacteria and other organisms that may be in the water,” the agency, known as GLWA, said.

GLWA initially said roughly two dozen cities and townships were affected by the boil recommendation. But it reduced the number when it learned that water pressure didn’t fall below a certain threshold in some areas, including Pontiac, Rochester Hills, Sterling Heights and Troy.

Flint said it switched to a different water source.

“Once the leak is isolated, crews will begin to open emergency connections to other mains in the system to restore some flow to the impacted communities,” the agency said.

At 4 p.m. Saturday, Governor Whitmer activated the State Emergency Operations Center, making all state resources are made available to support the local communities as they need it. So far, the SEOC is working to fulfill requests for bottled water. Conditions and needs will continue to be assessed, according to a press release from Michigan State Police.

News 8’s Anna Skog contributed to this report.