Source: Crane may not have lifted load properly, causing accident on 520 bridge that injured 8

SEATTLE -- An investigation was launched Wednesday into the construction accident at the State Route 520 bridge that sent an overhead sign crashing down on a Metro bus, injuring eight people.

The Washington State patrol said a crane dropped a large steep pipe that hit an overhead highway sign, which then crashed down on the bus.

The Washington State Department of Transportation announced that the contractor, Flatiron Construction, on Wednesday suspended all construction work while an investigation is under way.

The state Department of Labor and Industries said they cannot talk about an open case, but a source close to the investigation told Q13 FOX News that the load may have not been lifted properly.

With the damage to the bus severe and eight passengers hurt, the 911 calls poured in, including one from a construction worker on the site.

“The piling we were unloading hit the sign, the sign looks like it came down on the bus,” the caller said.

Drivers who witnessed the sudden impact rushed over to help passengers.

“There were people crying, people really shook up about it,” one witness said.

Labor and Industries is investigating Flatiron and two subcontractors doing the crane work when the accident happened. WSDOT released a statement that reads, in part.

“Last night’s incident was during a routine operation that has been performed safely and successfully many times by the contractor working on the SR 520 West Approach Bridge North Project since October 2014.”

But a source with knowledge of the accident told Q13 FOX News the crane was not plumb, meaning it wasn`t sitting directly above the load when it lifted the load off the flatbed truck, causing the pipe to swing and hit the sign.

“If you are going to do serious or potentially dangerous work on the bridge, close the bridge and then do all the work,” one driver said.

We tried to pose that question to Flatiron at its Bothell office but no one at the location could answer any questions.

But WSDOT says safety is a priority for them and the contractor.

Although WSDOT called the work routine, our source says it is “highly unusual” that traffic would be allowed to continue moving on the bridge while that type of work was taking place.