A school bus driver lost control of his vehicle, striking more than a dozen students as they left their high school Friday, then barreling down a road and into a retaining wall, officials said. Seventeen students were hospitalized, one in critical condition.

The driver reported that the vehicle developed a problem that left it "somewhat steerable but out of control," Pennsbury High School Principal William Katz said.

Fourteen injured students were on foot, while three were on the bus, officials said. The injuries ranged from minor to severe.

One boy dived under the bus as it veered toward him, suffering only scrapes and bruises.

"The bus drove over him while he was laying flat on his back looking up," said Lower Bucks County Hospital spokesman Bob Harris. "Thank goodness the buses are high."

The driver did not appear to suffer any medical problems and was taken to a police station for questioning, Falls Township Public Safety Director Neil Harkins said. Harkins said the driver was an older man who works for the school district.

"For reasons we don't understand, the driver lost control of the bus," said Pennsbury Superintendent Paul Long.

Students who saw the accident described a chaotic scene at the high school, which has two adjacent campuses.

The bus jumped a curb outside one of the school buildings, drove over a sidewalk, barreled down an access road, mowed down a fence and slammed head-on into the retaining wall. In all, the bus traveled about a half-mile.

Jeff Kardos, 14, of Yardley, said he saw a security guard drive alongside the bus to try to warn students to get out of the way. After it hit the wall, students scrambled out the back emergency door, said another student, 15-year-old Matthew Walters, of Levittown.

Kardos said the driver told him he had turned the key off and put the bus in gear in an attempt to control it, but could not bring it to a stop.

The accident occurred at about 2:20 p.m. as the students were being dismissed from the school, which is about 20 miles northeast of Philadelphia.

The injured were taken to St. Mary Hospital, Lower Bucks County Hospital and Frankford Hospital-Bucks, school officials said.

A 17-year-old girl in critical condition was being transferred to a Philadelphia hospital, St. Mary Hospital spokeswoman Kathleen Smith said. Four other students were in good condition and a sixth was treated and released.

Frankford Hospital-Bucks received a 17-year-old girl who had only minor injuries, spokeswoman Maria Slade said.

Ten students were taken to Lower Bucks, said Harris, the hospital spokesman. Nine were treated and released and one was being held for further tests.

He said family members and friends arrived to check on the injured students.

"I can tell you that nobody is happy," Harris said. "It's a very sobering gathering."