Just under 700,000 homes and businesses are without power in parts of Michigan and Ohio early Friday as a forceful round of severe thunderstorms has brought heavy rains, strong winds and at least one confirmed tornado to the region.

The storms marched from southern Michigan into Ohio overnight, threatening powerful wind gusts of up to 85 mph, hail up to 1.5 inches in diameter and possible tornadoes. Northern portions of Ohio are under flood watches until 8 a.m. ET Friday due to excessive rainfall.

A large and “extremely dangerous” tornado was confirmed near Williamston, Michigan, in Ingham County at about 9:30 p.m. Thursday, according to the National Weather Service Offices in Detroit and Grand Rapids.

No life-threatening injures were reported in Ingham County, according to Rob Dale with the county’s emergency management office. Fewer than 10 non-life-threatening injuries were sustained on the interstate, he said.

“Everyone in a house or a building was fine,” Dale said, noting that the roof of an assisted living center collapsed but everyone inside was safe and uninjured. Officials plan to reassess damage in the county during daylight hours.

The storms left 400,000 people without power in southern Michigan and nearly 300,000 in the dark in northern Ohio overnight, according to tracker PowerOutage.us.

A powerful gust of 70 mph was reported in Detroit Thursday night.

The storms come on the heels of an earlier round of heavy rainfall that wrapped up in southern Michigan and northern Ohio Thursday morning, bringing 7 to 8 inches in some places.

The earlier downpours halted incoming flights at the Detroit Metropolitan Wayne County Airport on Thursday and overnight flooding prompted closures of roadways. About 18% of flights originating at the airport were canceled on Thursday, though the roadways were reopened later in the day.