The Interstate 5 bridge spanning the Skagit River in Washington state collapsed Thursday evening, dumping two cars into the water. Three people were injured.

Authorities initially weren't sure how many people were involved or if there'd been any injuries or deaths. Shortly after the collapse, Washington State Trooper Mark Francis told CNN that he didn't expect a high casualty rate, in part because the bridge is located in a rural area and is rarely crowded.

The Associated Press interviewed a witness who saw at least three cars in the river.



CBS is reporting that the collapse was caused by an oversized semi-trailer truck, which hit a beam across the top of the bridge.

UPDATE: The Everett Herald is now reporting that just two cars were involved and that all three passengers have been accounted for.

UPDATE 2: The three people rescued were taken to a nearby hospital and treated for minor injuries. State transportation authorities still haven't determined the official cause of the accident, though it's believed a semi-trailer truck is responsible.

"We're looking at the cause being an oversized, over-height vehicle, striking critical portions of this bridge, causing it to collapse," said Travis Phelps of the Washington State Department of Transportation and Washington State Patrol.

The National Transportation Safety Board will arrive later today to investigate the collapse.

[Image via WJXT]