MOUNT VERNON, Wash. (AP) - The Washington State Patrol chief says the Interstate 5 bridge collapse into the Skagit River at Mount Vernon was caused by an oversize truck.

Chief John Batiste told an overnight news conference that the truck hit an overhead span. The truck made it off the bridge and the driver remained at the scene and cooperated with investigators.

Two other vehicles went into the water Thursday evening as the bridge collapsed. Three people were rescued and are recovering.

Officials said drivers should expect delays at the break in the major north-south highway about 60 miles north of Seattle. Detours have been set up to try to ease the congestion.

The scene of a bridge collapse int the Skagit River on Interstate 5 is pictured May 23, 2013 near Mt. Vernon, Washington. People and cars were thrown into the river when the four-lane bridge collapsed. At least three people were rescued from the water but there have been no reported deaths. Police are investigating witnesses reports that a semi-truck may have struck the bridge causing the collapse. (Stephen Brashear/Getty Images)
Crews survey the scene of a bridge collapse on Interstate 5 on May 23, 2013 near Mt. Vernon, Washington. I-5 connects Seattle, Washington to Vancouver B.C., Canada. No deaths have been reported, and three people were taken to hospitals with injuries. (Stephen Brashear/Getty Images)
Crews survey the scene of a bridge collapse on Interstate 5 into the Skagit River May 23, 2013 near Mt. Vernon, Washington. People and cars were thrown into the river when the four-lane bridge collapsed. At least three people were rescued from the water but there have been no reported deaths. Police are investigating witnesses reports that a semi-truck may have struck the bridge causing the collapse. (Stephen Brashear/Getty Images)
Crews survey the scene of a bridge collapse on Interstate 5 into the Skagit River May 23, 2013 near Mt. Vernon, Washington. People and cars were thrown into the river when the four-lane bridge collapsed. At least three people were rescued from the water but there have been no reported deaths. Police are investigating witnesses reports that a semi-truck may have struck the bridge causing the collapse. (Stephen Brashear/Getty Images)

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