A duck boat involved in a deadly Seattle traffic crash did not have an axle repair that was recommended for the amphibious vehicle in 2013, the National Transportation Safety Board said Sunday.
NTSB member Earl Weener said investigators only recently learned that Ride the Ducks International issued the warning about potential axle failure and recommended a specific repair two years ago. But he said the boat involved in Seattle crash didn't have the fix.
It's unclear if the company that owns the vehicle — Ride the Ducks of Seattle — was aware of the warning, Weener said at a news conference.
A representative of the Seattle duck tour company said he did not have any immediate comment on the NTSB's account.
The crash last week between the duck boat and a charter bus left four international college students dead.
Investigators said Saturday that the left front axle of the duck boat was sheared off, but they hadn't determined if that damage happened before the collision or during it.
About 45 students and staff from North Seattle College were on the bus on the Aurora Bridge when the tourist-carrying duck boat swerved into it.
More than 50 people were taken to hospitals. At least 16 people remained at Seattle hospitals Sunday, with five in intensive care and one in critical condition.
The amphibious vehicle tours are offered around the world, including in Philadelphia; Austin, Texas; Miami; Fort Lauderdale, Fla.; and London.
The federal probe is expected to take months.
It's the first time the NTSB has looked into a land crash of the amphibious vehicles, which critics say are too dangerous for city streets. The federal agency has scrutinized duck tour vehicles several times when they've been in accidents on water.
State regulators also have opened an investigation, which entails inspecting all vehicle and driver records.
The amphibious vehicle involved in the crash — known as Duck No. 6 — underwent regular annual examinations by a federally certified inspector, most recently in 2015 and 2014, and met federal standards, Washington Utilities and Transportation Commission spokeswoman Amanda Maxwell said.
Ride the Ducks International refurbished the vehicle in 2005.