Pennsylvania ? A school bus driver lost control and struck several students as they left a high school Friday, then crashed into a retaining wall, sending 17 students to hospitals, officials said.

The driver said the bus developed some sort of mechanical problem that left it “somewhat steerable but out of control,” Pennsbury High School Principal William Katz said.

Fourteen students on foot and the three on the bus were taken to hospitals, officials said. A 17-year-old girl in critical condition was being transferred to a hospital in Philadelphia, a hospital spokeswoman said.

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

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 into a retaining wall. In all, the bus traveled about a half-mile.