A passenger bus plunged off a highway and rolled 500 yards down a hillside in western Honduras on Tuesday, killing 26 people and injuring at least 19, authorities said.

Emergency personnel worked to free people from the twisted wreckage near the border with El Salvador.

"This is a terrible tragedy that will cause mourning in a lot of poor families," Carlos Cordero, the head of the national firefighters force, said in a telephone interview. "We are making superhuman efforts to rescue survivors."

The 26 dead included at least three children and 16 women, all thrown from the bus by the force of the crash. Several of the injured were in serious condition, Cordero said.

The accident happened on a stretch of highway so high and treacherous that it is known as "The Angel's Flight."

Investigators said mechanical problems may have played a role in the crash.