Updated

A bus carrying Swedish high school students to a ski resort crashed Sunday in central Sweden, killing three people and injuring 20 others — seven of them seriously, rescue officials said.

The 52 students were en route to a ski resort with seven adults, including the driver, when the accident occurred on a main highway south of Sveg, a small town 430 kilometers (260 miles) northwest of the capital, Stockholm.

The cause of the accident was not immediately known, but the road reportedly was icy when the accident occurred about 7 a.m. (0500 GMT). Pictures showed the bus lying on its side in a ditch beside the highway.

Rescue services spokesman Peter Nystedt said some 30 others sustained minor injuries.

The father of Stina Almqvist, one of the students on the bus, said he was awakened by a call from his "panic-stricken" daughter.

"She just screamed and screamed," Fredrik Almqvist told the Expressen tabloid. "I can still hear her screams."

Friends of the students from Angskolan high school in Skene gathered at the school on Sunday.

A priest from a nearby church in town in the southwest Sweden, Goran Landgren, told reporters at the school that the accident had "deeply upset them all."

Prime Minister Stefan Lofven said the accident "leaves me and the whole country in sorrow."