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DENVER (KDVR) — A Chicago law firm has filed more lawsuits on behalf of passengers who watched their United Airlines engine burst into flames shortly after takeoff, causing plane debris to fall on the Denver metro.

The Clifford Law Office, a personal injury firm in the same city as United’s headquarters, says the four passengers experienced emotional trauma from the Feb. 20 engine explosion and emergency landing.

“There was a very terrifying descent for about 24 minutes until they got on the ground,” said Richard F. Burke Jr., a partner at the firm that also represents families in the Boeing 737 MAX crash that killed 157 people in Ethiopia two years ago.

United Airlines 328 was leaving Denver for Honolulu when an explosion happened just four minutes after takeoff. Passengers could see the Boeing 777-200’s right engine in flames.

“This type of event has to be prevented because, obviously, the flying public….they’re relying on airlines to operate safe planes, and the airlines have a responsibility to make sure they have proper and adequate inspections and maintenance plans to prevent engine failure of this type,” Burke said.

Burke said the firm expects to file more lawsuits, possibly as soon as Wednesday. They had already filed lawsuits on behalf of two other passengers earlier this month.

A preliminary report from the National Transportation Safety Board found the plane’s fan blades were fractured. It could take more than a year for the NTSB to finish its investigation.

In a separate lawsuit filed in March, another passenger is seeking class-action status.