OLYMPIA, Wash. — State regulators are — for now — denying a request from a Seattle tour company to once again begin using the type of duck boats involved in a 2015 crash that killed five college students and injured dozens more.

The Utilities and Transportation Commission said Tuesday that Ride the Ducks of Seattle has not shown that the amphibious “stretch duck” boats are safe.

One of the company’s vehicles collided with a charter bus on Seattle’s Aurora Bridge in 2015, resulting in the deaths of five people. Regulators suspended the company’s operating permit but later allowed it to begin using another type of tour boat, which it refers to as “truck ducks.”

On July 12, the company asked for permission to begin running its stretch boats again, saying that it intended to replace the front axles when the parts become available. The UTC denied that request but said it would reconsider if the company demonstrates that the vehicles meet safety standards.