America's transport safety watchdog has warned that the Washington state bridge collapse is a wake-up call for the country.
"This is a really significant event and we need to learn from it, not just in Washington but around the country," Debbie Hersman chairman of the National Transportation Safety Board, said after taking a boat ride on the Skagit River below the dramatic scene.
A truck bumped against the steel framework on Thursday, collapsing the Interstate 5 bridge and sending two vehicles and three people into the chilly water.
Investigators need to find out what happened in Washington and if it could be repeated at similar bridges around the country, Ms Hersman said. "At the end of the day it's about preventing an accident like this," she added.
Her team will spend a week to 10 days looking at the bridge, talking to the truck driver whose vehicle hit it, and examining maintenance documents and previous accident reports.
Other over-height vehicles struck the Skagit River bridge before the collapse, she noted. Investigators are using a high tech 3-D video camera to review the scene and attempt to pinpoint where the bridge failure began.
Ms Hersman did not expect the investigation to delay removal of debris from the river or work on a temporary solution to replace or repair the bridge. State and government officials could and would work together on the investigation, she said.
They willl be watching for safety issues that could affect other bridges. "The results can be very catastrophic," Ms Hersman said. "We're very fortunate in this situation."
State authorities said it would take time to find short and long-term fixes for the bridge that collapsed.
While NTSB finishes its inspection, state workers will begin removing debris from the river. Next, a temporary solution will be put in place to return traffic to Washington state's most important north-south road.