SEATTLE >> Washington state regulators suspended the operations of a Seattle tour company Monday after one of its amphibious vehicles swerved into an oncoming charter bus last week, killing five people and hurting dozens of others.

The state Utilities and Transportation Commission met in an emergency session to keep the repurposed military "duck boats," owned by Ride the Ducks of Seattle, off the streets pending inspections and a review of driver and maintenance records.

The decision came a day after federal investigators announced that the duck boat involved in the crash did not have an axle repair that was recommended two years ago for such vehicles. Authorities are looking into whether axle failure caused the crash; the vehicle’s front left axle was found sheared off, but it’s not clear if it broke before the collision or during it.

Early indications are that despite a service bulletin issued in 2013 by Ride the Ducks International, the Seattle firm had not repaired axles on any of its vehicles, said David Pratt, the commission’s assistant director for transportation safety.

"Because of the possibility of continuing safety problems and a current lack of confidence surrounding the company’s operations, we believe it is important to act immediately to protect the public safety," commission chairman David Danner said.

Brian Tracey, owner of Ride the Ducks of Seattle, said Sunday night that he was in "complete agreement" with keeping the boats parked pending the inspections. He did not address whether he had known of the 2013 bulletin before the crash.

"We will not return any of the fleet to service until we can demonstrate that our fleet is well-maintained, road-worthy and safe through an independent inspection of every Duck vehicle we operate," he said.

Atlanta-based Ride the Ducks International refurbished the 1945 Army surplus vehicle involved in the crash and sold it to Ride the Ducks of Seattle, an independently owned licensee, in 2005. It said in a written statement Monday that it warned its customers in 2013 about potential failure of the front axle housing assembly on 57 vehicles in service around the country, and it recommended specific inspections and repairs to reinforce the housing.

Its other affiliates and licensees — in Philadelphia; Stone Mountain Park, Georgia; Branson, Missouri; and Newport, Kentucky — had all complied, the company said.

"We had no reason to believe that Seattle had not complied with the bulletin," the statement said.

Witnesses described seeing the duck boat’s left front tire lock up or otherwise have mechanical problems Thursday before it veered into the bus. It could take a year to determine the cause of the crash, the National Transportation Safety Board said Sunday.

Four international college students died at the scene, and a fifth — identified as a 20-year-old woman — died Sunday. They were among about 45 students and staff from North Seattle College who were on the bus when the tourist-carrying duck boat swerved into it on the Aurora Bridge, a six-lane span with no median barrier.

More than 50 people were taken to hospitals. At least 13 people remained hospitalized.

The state transportation commission said it did not learn of the warning until last weekend and that Ride the Ducks of Seattle had no legal obligation to report it.

"If I had received it, we would have immediately contacted the company and worked with them to talk about the repairs that were needed repairs or the seriousness of it," Pratt said.

The amphibious vehicle tours operate around the world, including in Boston; Philadelphia; Austin, Texas; Miami; Fort Lauderdale, Florida; and London. Tour companies in Boston and Miami said Monday that their vehicles are different from Seattle’s and were not subject to the 2013 service bulletin.