UPDATED -- A bridge along Interstate 5 in Washington state partially collapsed Thursday evening, closing part of the route, with the state and the trucking company involved blaming each other today.

It happened around 7 p.m. PDT near Mount Vernon, north of Seattle, with a section of both the northbound and southbound lanes plunging into the Skagit River. I-5 connects with Highway 99 in British Columbia, Canada.

State police say a truck carrying an oversize load struck the overhead part of the span, leading to the collapse, with the truck and its occupants making it off the bridge. Two vehicles went into the water about 50 feet below with three people being rescued. They reportedly were taken to an area hospital and are reported to be in stable condition.

In an interview with the Associated Press the Canadian trucking company involved, Mullen, said it had a permit issued by Washington state to move the load across the bridge and used local escorts to help in the navigation.

The Washington Department of Transportation says traffic is being diverted off southbound I-5 at Exit 230. For an alternate route, take eastbound SR 20, then south on S. Burlington Blvd. and west on E. College Way (SR 538) to southbound I-5. 

Northbound I-5 traffic must exit at Exit 227. An alternate route is east to E. College Way to northbound Riverside Drive-S. Burlington Boulevard, then west on George Hopper Road to I-5. 

To use SR 9 as an alternate northbound route, bypassing Mount Vernon, take Exit 221 at SR 534 east to northbound SR 9 to SR 20 westbound to I-5.

The National Transportation Safety Board has dispatched a "go team" to the site to investigate the collapse.

Published reports say the span was built in 1955 and carries more than 70,000 vehicles per day.

Washington state was given a C by the American Society of Civil Engineers in its 2013 infrastructure report card and a C- when it came to the state's bridges. The group says than a quarter of Washington's more than 7,800 bridges are considered structurally deficient of functionally obsolete.

A Federal Highway Administration database shows the bridge is rated as functionally obsolete, meaning that its design is outdated and unable to handle the traffic demands placed upon it.