*Governor Jay Inslee said Friday federal transportation officials were helping find a temporary structure known as a Bailey bridge to span the 160-feet of missing section of bridge.
*The Canadian trucking company involved in a Washington state bridge collapse says it received a state-issued permit to carry its oversized load across the bridge.
*An emergency proclamation from Governor Inslee said the estimated cost to repair the bridge is $15 million.
*Inslee also declared a state of emergency in Skagit, Whatcom, and Snohomish Counties because of the impact on citizens.
*Three people and their vehicles went into the water, but all survived.
*Detours are in place, but drivers are urged to avoid the area.
MOUNT VERNON, Wash. -- Washington Governor Jay Inslee said federal transportation officials are helping find a temporary structure to span the 160-foot section of an Interstate 5 bridge that collapsed into the Skagit River Thursday night, paralyzing the main north-south corridor between Seattle and Canada.
"There is a possibility we can use what's known as a Bailey bridge, which was something that was built and developed in World War II to span this 160-foot section," said Inslee. "We are searching the entire country right now, trying to find a Bailey bridge that might be able to provide us with a temporary span."
The collapse happened around 7 p.m. Thursday on the north part of the four-lane Interstate 5 bridge near Mount Vernon, about 60 miles north of Seattle. It sent a section of the span and two vehicles into the Skagit River below, though all three occupants suffered only minor injuries.
Governor Inslee declared a state of emergency for Skagit, Snohomish and Whatcom Counties. Inslee said estimates to repair the bridge were $15 million.
Initially, it wasn't clear if the bridge just gave way on its own. But at an overnight news conference, Washington State Patrol Chief John Batiste blamed it on a tractor-trailer carrying a tall load that hit an upper part of the 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 about 25 feet below as the structure crumbled. The three people were rescued and were recovering Friday.
"For reasons unknown at this point in time, the semi struck the overhead of the bridge causing the collapse," he said.
The trucking company involved says it received a state-issued permit to carry its oversized load across the bridge.
Ed Scherbinski is vice president of Mullen Trucking in Alberta. He said in an interview with The Associated Press that the Washington state Department of Transportation had approved of the company's plan to drive a piece of drilling equipment along Interstate 5 to Vancouver, Wash.
He also said the company hired a local escort to help navigate the route. He said the driver was well-experienced with handling oversized loads.
"This is what we do for a living. We pride ourselves in doing things the proper way," said Scherbinski
Mike Allende, a state DOT spokesman, confirmed the truck had its permit.
"We're still trying to figure out why it hit the bridge," he said. "It's ultimately up to the trucking company to figure out whether it can get through. It's their responsibility to make sure the load they have can travel on that route."
Washington State Patrol said the truck was carrying a large steel box that contained drill parts, and the box struck the bridge girders.
Scherbinski said company officials are as bewildered as everyone else. He said he's not sure whether the Mullen Trucking vehicle was the cause of the collapse, but the driver could see the bridge falling in his rearview mirror.
The truck made it off the bridge and the driver remained at the scene and cooperated with investigators. The driver has been identified as a 42-year-old man from Alberta, Canada. He was driving for Mullen Trucking. Trooper Mark Francis told the Skagit Valley Herald that the truck was hauling drilling equipment.
Cynthia Scott, of Spruce Grove, Alberta, said she spoke with her husband moments after he saw the bridge fall into a river in his rear-view mirror. Cynthia Scott said there was a small ding in one of the front corners of the load.
Dave Chesson, a state DOT spokesman, said there were no signs leading up to the bridge warning about its clearance height.
Traffic could be affected for some time. The bridge is used by an average of 71,000 vehicles a day, so the roadblock will cause a major disruption in trade and tourism between Seattle and Vancouver, British Columbia.
Detours have been set up to try to ease the congestion. Batiste urged drivers to avoid the area if possible, especially over the Memorial Day weekend.
"The I-5 corridor is totally disrupted," said Washington Gov. Jay Inslee, who went to the scene Thursday night.
"Thanks to the rescuers and a little bit of luck, we had three Skagitonians who made it out of the Skagit River alive," Inslee said.
Dan Sligh and his wife were in their pickup on Interstate 5 heading to a camping trip when a bridge before them disappeared in a "big puff of dust.”
"I hit the brakes and we went off," Sligh told reporters from a hospital, adding he "saw the water approaching ... you hold on as tight as you can.”
Sligh, his wife and another man in a different vehicle were dumped into the chilly waters of the Skagit River.
Sligh and his wife were taken to Skagit Valley Hospital with non-life-threatening injuries. The other man was reported in stable condition at United General Hospital in Sedro-Woolley, hospital CEO Greg Reed said.
Sligh said his shoulder was dislocated in the drop into the water, and he found himself "belly deep in water in the truck." He said he popped his shoulder back in and called out to his wife, who he described as being in shock initially as they waited for rescuers to arrive in boats.
The bridge was inspected twice last year and repairs were made, Transportation Secretary Lynn Peterson said.
"It's an older bridge that needs a lot of work just like a good number of bridges around the state," she said.
Transportation officials are working on plans for either a temporary or permanent replacement, she said.
The National Transportation Safety Board was sending an investigative team.
Jeremiah Thomas, a volunteer firefighter, said he was driving nearby when he glimpsed something out of the corner of his eye and turned to look.
"The bridge just went down, it crashed through the water," he said. "It was really surreal.”
Deyerin said the water depth was about 15 feet, and the vehicles half-visible in the water likely were resting on portions of the collapsed bridge.
Crowds of people lined the river to watch the scene unfold.
Bridge listed as 'functionally obsolete'
The bridge is not considered structurally deficient but is listed as being "functionally obsolete" - a category meaning that their design is outdated, such as having narrow shoulders or low clearance underneath, according to a database compiled by the Federal Highway Administration.
The bridge was built in 1955 and has a sufficiency rating of 57.4 out of 100, according to federal records. That is well below the statewide average rating of 80, according to an Associated Press analysis of federal data, but 759 bridges in the state have a lower sufficiency score.
According to a 2012 Skagit County Public Works Department, 42 of the county's 108 bridges that are 50 years or older. The document says eight of the bridges are more than 70 years old and two are over 80.
Washington state was given a C in the American Society of Civil Engineers' 2013 infrastructure report card and a C- when it came to the state's bridges. The group said more than a quarter of Washington's 7,840 bridges are considered structurally deficient of functionally obsolete.
Liza Javier and Travis Pittman of KING 5 and Manuel Valdes and Mike Baker of The Associated Press contributed to this report.