(BUTLER COUNTY, Ohio) -- More than 30 people were injured after a Greyhound bus overturned on an Ohio interstate early Saturday, authorities said. The bus was heading northbound on I-75 in Butler County, Ohio when it overturned shortly after 4 a.m., Butler County Emergency Operation Center officials said in a news release. "The bus started shaking...and we hit a tree then after we hit the tree we rolled... at least twice," said passenger Christopher Lake.
The bus was carrying 52 people. Thirty four people were transported to area hospitals, including six people who were air lifted. Four of the injured are labeled in critical condition and 12 are in serious condition according to authorities. The cause of the accident has not been determined.
Copyright 2013 ABC News Radio