MOUNT VERNON, Wash. - An Interstate 5 bridge over a river north of Seattle collapsed Thursday evening, dumping vehicles and people into the water, the Washington State Patrol said.

The four-lane bridge over the Skagit River collapsed about 7 p.m., Trooper Mark Francis said. There was no immediate estimate of how many people were in the water or whether there were any injuries or deaths, he said.

It also was not known what caused the collapse of the bridge about 60 miles north of Seattle.

Xavier Grospe, 62, who lives nearby, said he could see three cars with what appeared to be one person per vehicle. The vehicles were partially submerged, and the apparent drivers were sitting either atop the vehicles or on the edge of open windows. "It doesn't look like anybody's in danger right now," Grospe said.

Crowds of people lined the river to watch the scene unfold, the Skagit-Valley Herald reported.