DENVER — Police told The Denver Post that they have found no signs of mechanical issues with the school bus that crashed at the airport earlier this month, injuring 18 passengers and killing the bus driver.

As previously reported, the bus driver, Kari Chopper, made a left turn to return to the terminal loop instead of a right turn to leave the Denver International Airport, and drove off the road and into a pillar. The bus was traveling at 30 miles per hour to 40 miles per hour at the time. The speed limit on the road that the bus was traveling on is closer to about 15 miles per hour, and it is unclear why the bus was there.

Investigators told the newspaper that they still don’t know why the bus crashed. Doug Schepman, a spokesman for the Denver Police Department, told The Denver Post that an autopsy for Chopper has not been released yet. However, Chopper’s husband told the newspaper that an official at Denver’s medical examiner’s office said that she had an enlarged heart.

Police said there is no indication that the crash was intentional, although they have not ruled that out, and that they are looking into whether Chopper had a medical condition, according to The Denver Post. Investigators also said that some details about the crash may never be clarified because the driver died at the scene.

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