CNN — Dan Sligh could see it coming. An 18-wheeler carrying an oversize load had just struck part of the Interstate 5 bridge over Washington's frigid Skagit River. And the pavement was giving way.
He slammed on the brakes, but the momentum of his truck and trailer carried Sligh and his wife off the bridge and into the water dozens of feet below, he told CNN affiliate KOMO Thursday, hours after the incident some 60 miles north of Seattle.
"You hold on as tight as you can," Sligh said. Then, a "white flash and cold water."
The impact dislocated his shoulder, but the Navy veteran just popped it back in and dragged his unresponsive wife to safety.
Another driver also fell from the bridge, according to state officials. Amazingly, no one died.
"Rough day," Sligh told KOMO. "Glad to be here breathing."
About a fourth of the bridge's 1,100-foot span collapsed, CNN affiliate KIRO reported. While drivers can take alternate routes, the collapse will cause traffic snarls, state officials warned.
The bridge carries about 77,000 cars a day, according to the Washington State Department of Transportation.
It had been rated "functionally deficient," according to a federal database, but the cause of the collapse is under investigation, the agency said. State police and a federal transportation safety team are joining the state transportation agency in the probe.
At least one factor could be that truck accident.
Sligh told KOMO he was traveling south on the interstate when he realized that a load being carried by a tractor-trailer in front of him appeared to be about four feet too wide to fit through the bridge's superstructure.
"Anytime he wants to go over to the left would be OK," Sligh said he told his wife.
But another tractor-trailer appeared to hem the truck in to the right lane.
"There was a big puff of dust, and I hit the brakes."
Dale Ogden told CNN affiliate KING that he was driving near the tractor-trailer's pilot car when he saw a device on that car designed to indicate whether a truck can clear an obstacle hit the top of the bridge.
He then watched in his rear-view mirror as the truck struck the bridge, he told KING.
"It almost tipped the truck over but it came back down. It tipped it up to about a 30 degree angle to the left and it came back down on its wheels, and almost instantaneously behind that I saw girders falling in my rear-view mirror," he said.
The truck's driver was questioned but not detained, state police said.
Investigators are seeking more witnesses to the collapse, Washington State Police Trooper Mark Francis said.
The bridge was built 1955, according to KOMO, and was listed by the Federal Highway Administration as "structurally deficient."
That designation means parts of a bridge require monitoring or repair, but does not indicate the bridge is unsafe or likely to collapse, according to the agency. Most deficient bridges remain open to traffic, the agency says.
The number of bridges the state's transportation department considers structurally deficient has grown nearly 50% in the past six years, according to a 2012 government report.
President Barack Obama in late March called for Congress to provide $21 billion for infrastructure construction, including improvements to existing roadways.