HUNTSVILLE, Alabama — A fourth high school student has died from injuries she got in when a school bus nose-dived off an interstate overpass, the police chief said yesterday.The bus driver, who was found critically injured on the overpass, was among 15 who remained hospitalised, authorities said. Four were listed as critical.

Police Chief Rex Reynolds identified the fourth victim of Monday’s school bus wreck as Crystal Renee McCrary, 17. Like the other victims, she was a student at Lee High School who was on the bus when a car came up in a side lane and the bus veered over the guardrail and crashed about 30 feet below.

Debbie Hersman, a spokeswoman for the National Transportation Safety Board, said investigators were trying to determine how the driver ended up on the overpass, escaping the devastating impact that crumpled the front of the bus.

Two teenage girls died in the wreckage; a third died later at a hospital. More than 30 students were injured.

“The bus went to the side, and I guess it went over,” passenger LaWanda Jefferson said. “When it was falling ... I was just glad when it hit the ground.”

“They were falling on each other. People were screaming, yelling, crying,” said Jefferson, 16, who suffered fractures to her left arm and cuts and bruises to her face. Five people, including the bus driver, had undergone surgery.

Police said the bus, taking students to classes at a downtown tech centre, swerved on the overpass, plowed through a barrier and plunged to the street.

Reynolds said an orange Toyota Celica driven by another Lee High student apparently came close to or struck the bus, causing it to swerve.

There is “some contact evidence,” Hersman said, noting that investigators were looking for paint transfers between the vehicles.