Updated at 4:50 p.m. ET
A multi-vehicle accident involving a charter bus, a duck boat and two cars in central Seattle has left at least four people dead and several injured, authorities say.
"The crash occurred shortly after 11:11 a.m., blocking all lanes of the state Route 99 bridge. Fire crews were on the scene and drivers were directed to use alternate routes. ...
"Damage to the tour bus appeared extensive. Authorities had yet to say what caused the crash. It appeared as though the bus and the duck boat were both traveling south on the bridge."
Lt. Sue Stangl of the Seattle Fire Dept. said it was her understanding that "the majority of the significant injuries occurred on the bus" and that included two fatalities. Officials later said four had died.
"When (firefighters) arrived a lot of people were running at them, obviously saying people needed help," Stangl said.
She said that first responders were able to remove everyone from the bus and that those with minor injuries were still being treated and moved from the scene.
Seattle's King TV reports:
"At least 50 people have been evaluated at the scene.
"The force was so powerful, a huge gash was ripped in the side of the bus.
"Because they are designed to travel on the road and on water, the hull of the ducks vehicle is stronger than most buses on the road. Ride The Ducks says on its website their vehicles have no seat belts."
John Mundell, told The Associated Press that he was at the south end of Aurora Avenue bridge when he heard the crash.
The side of the charter bus was ripped open from the force of the collision, he said.
"We could hear the screech and twisted metal," he told AP. "It was surreal."
Mundell said he saw what appeared to be a few dozen people on the ground. "I wanted to try to help. I felt helpless."
Member station KUOW in Seattle has full coverage here.