FARGO, N.D. (AP) — A downpour flooded the Fargo area, closing a major highway early Tuesday and knocking out power for thousands of customers.

Hundreds of people were stuck when their vehicles stalled in flooded streets, and abandoned cars littered a stretch of about 10 blocks along a major east-west thoroughfare.

Sections of Interstate 29 north and south of Fargo were closed by high water, and that affected traffic on east-west I-94.

The floor of the Fargodome, the city's major arena, was flooded 6 feet deep.

About 7 inches of rain fell in six hours overnight, said Mayor Bruce Furness.

City officials declared a state of emergency. The metropolitan area, which includes Moorhead, Minn., has a population of around 100,000.

The main concern in Moorhead was a large runoff holding pond that was overflowing at Moorhead State University, said Dean Palmer, an office assistant in the school's physical plant.

Crews were sandbagging the pond. "If that were to go, you'd be in serious trouble. There'd be a lot of homes that would be gone," Palmer said.

Moorhead State had water in some buildings and canceled classes.

Flooded utility substations in Fargo blacked out some 20,000 customers during the night, but service was restored to most within about three hours, Northern States Power Co. officials said.

Water also threatened archives at the library of North Dakota State University, and Blue Cross Blue Shield of North Dakota had to close its main headquarters in Fargo as well as two Medicare operation centers.

"Crews are trying to protect the main computers and shut them down," said Blue Cross spokesman Larry Gauper.

Eastern North Dakota already had been saturated by about a week of rain.

Residents of Manvel, north of Grand Forks, have been battling flooding from the Turtle River for about a week. Grand Forks, the state's third-largest city, was devastated by flooding from the Red River three years ago.