The major link between the US and Canadian sides of the Pacific Northwest region was severed after a bridge collapsed, dumping a handful of vehicles and people into a river, police said.
All three people who were on the span were rescued and taken to hospitals.
The four-lane Interstate 5 bridge — more than half a century old — collapsed about halfway between Seattle and Vancouver, British Columbia, Washington State Trooper Mark Francis said.
It was caused by an oversize truck hitting the span, the Washington State Patrol chief said.
“For reasons unknown at this point in time the semi struck the overhead of the bridge, causing the collapse,” Chief John Batiste told an overnight news conference.
The truck made it off the bridge and the driver remained at the scene and cooperated with investigators.
The collapse came at the start of one of the busiest holiday weekends of the year in the US, Memorial Day weekend.
The collapse came before sundown on a clear day.
The state Transportation Department said it was investigating whether an oversize truck load may have struck the bridge.
Dan Sligh and his wife were in their pickup truck on Interstate 5 heading to a camping trip when the bridge before them disappeared in a “big puff of dust.”
Sligh, his wife and another man in a different vehicle were dumped into the chilly waters of the Skagit River when the span collapsed on Thursday evening. They were injured, but authorities said it appeared nobody was killed in the bridge failure that raised questions about the safety of aging spans.
“We don’t think anyone else went into the water,” said Marcus Deyerin, a spokesman for the Northwest Washington Incident Management Team. “At this point we’re optimistic.”
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 chief executive officer Greg Reed said.
Authorities were trying to determine what caused the bridge to collapse about 100km north of Seattle in Skagit County.
Traffic along the heavily traveled route could be affected for some time.
“The I-5 corridor is totally disrupted,” said Governor Jay Inslee, who went to the scene on Thursday night.
The National Transportation Safety Board was sending an investigative team.
Francis said a portion of the four-lane bridge over the Skagit River collapsed about 7pm.
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.”
The bridge was about 15m above the water.
Deyerin said it appeared that two vehicles — a car and the pickup with the travel trailer attached — fell into the river.
He said the water depth was about 4.5m, and the vehicles half-visible in the water were likely resting on portions of the collapsed bridge.
Crowds of people lined the river to watch the scene unfold.
“It’s not something you see every day,” said Jimmy O’Connor, the owner of two local pizza restaurants who was driving on another bridge parallel to the one that collapsed.
The bridge was not classified as structurally deficient, but a US Federal Highway Administration database listed it as being “functionally obsolete” — a category meaning that the design is outdated, such as having narrow shoulders and low clearance underneath.