Holiday revelers looking forward to the Memorial Day Weekend are being advised to work around their travel itineraries as authorities expect a massive holiday-related traffic jam following the collapse of a portion of the Interstate 5 Skagit River Bridge in Washington, US on Thursday evening.

According to estimates of AAA Washington, about 34.8 million Americans journey 50 miles or father more from their home during the three-day weekend. "Certainly this kind of incident for people traveling on I-5 will have an impact," David Overstreet, a spokesman for AAA Washington, was quoted by Seattle Times.

"This is certainly a tragedy. It's a reminder that we need to take care of our transportation infrastructure before more of these things happen," he said.

Not only Americans going north will be affected, but also Canadians coming down south.

"It's going to impact everybody - business and nonbusiness," Bob Lama, a board member of the Mount Vernon Chamber of Commerce, said. "The Department of Transportation has their work cut out for them to figure out what to do. I imagine it will be many weeks until there's a fix."

On Thursday just after 7pm, the Interstate 5 Skagit River Bridge, located 100 kilometres north of Seattle, collapsed, hurtling cars and people into the water.

According to a tweet by Washington State Patrol trooper Mark Francis, both the four-lane bridge's north-bound and south-bound lanes dropped into the river.

Burlington Mayor Steve Sexton said the incident will not only affect travel time in the nearby localities but also businesses.

"This is the main thoroughfare for traffic and commerce going from Seattle to Vancouver," said Burlington Mayor Steve Sexton. "It's a far-reaching effect."

"This is going to affect us not only this Memorial Day weekend, but long into the future," Mr Sexton added.

One motorist interviewed by the Skagit Valley Herald said he felt a vibration.

"I thought something was wrong with my car at first," he said. When he looked in his rear view mirror, he saw the section of bridge he had just crossed was no longer there.

Rescue teams continued to pull-out people as well as cars from the river.