LITCHFIELD – A blown tire likely caused a double-decker bus to lurch out of control and strike a bridge pillar in the grassy median of an interstate highway, killing one passenger and injuring nearly four dozen others, an Illinois State Police investigator said Friday.

A fully packed Megabus crashed head-on into the concrete pillar Thursday afternoon on Interstate 55 near Litchfield, about 55 miles northeast of St. Louis. The front of the bus was so mangled rescuers had to use ladders to pull people out windows of the upper level.

Passengers gave harrowing accounts of the wreck: people screaming, blood in the aisles, injured passengers tossed about. Several reported hearing a tire blow out just before the crash, and Illinois State Police Lt. Louis Kink said that likely was the cause.