Investigators from the National Transportation Safety Board are interested in the front left axle of an amphibious "duck boat" involved in an accident on a Seattle bridge Thursday that killed four college students.
"The front axle was sheared off — for what reason yet we don't yet know," NTSB board member Earl Weener told reporters Saturday, although he said it is too early to determine a cause of the 11:15 a.m. crash on the Aurora Bridge.
The crash killed four international students from North Seattle College who were aboard a charter bus that collided with the 1945 DUKW military-style vehicle owned by Ride the Ducks of Seattle.
The charter bus carrying the students and the duck boat tour vehicle were traveling in opposite directions on the Aurora Bridge when the accident occurred.
A witness behind the duck boat told NBC station KING5 that the duck boat was moving into the left lane when "it seemed to lurch suddenly" before striking another vehicle and then slamming into the bus.
"I saw a bunch of smoke and what appeared to be the front left wheel pop off, and then it clipped a smaller SUV and basically almost T-boned into the oncoming bus and spun around," Jesse Christenson said Thursday.
The amphibious vehicle was refurbished in 2005 for its engine and chassis, Weener said. State officials have said the Ride the Ducks fleet was inspected in 2012, and passed.
Weener said the axle and parts of the drive mechanism would be sent to the NTSB labs in the hope of understanding the characteristics of the fracture and whether it contributed to the crash, or whether it occurred before or after the crash.
"It's way too early to say anything about a probable cause," Weener said.