RCMP say driver confusion may have contributed to Friday's fatal bus crash in New Brunswick. The accident killed two boys and two girls who were on their way from Massachusetts to Halifax.

About 30 people suffered minor injuries when the bus overturned on the Trans-Canada Highway near Sussex. Most of the injured have been released from hospital.

The crash happened at about 4:30 a.m. Atlantic Time in good weather.

RCMP say the driver apparently missed the off-ramp he was supposed to take. Instead, he took the next ramp one that had a sharp curve.

The bus went out of control, hit the ditch, and rolled down a hill before landing on its side.

There were 42 children, mostly 12- and 13-year-olds, and seven adults on the bus, according to RCMP Staff Sgt. Dave Brown. Many of the passengers were asleep when the bus went off the road.

The children were on their way to Nova Scotia as part of an exchange program. They attend a music program at Oakhill Middle School in Newton, Mass., according to Marvin Shapiro, principal of the school.

"They were going to Gaetz Brook (junior high school) outside of Halifax for a joint concert tonight and were going to be in a band festival in Halifax on Sunday," Shapiro said.

One of the parents, Thomas Mountain of Newton, Mass., said his 12-year-old son was on the bus and called him within an hour of the accident to say he was okay.

Students from Gaetz Brook visited Newton last year. The reaction at the Gaetz Brook school was one of shock and grief.

"We had a dance scheduled, a pot luck supper and we rented the local arena for a public performance of the combined bands," said Joe Fisher, principal of Gaetz Brook school.

Officials in Newton, a town of 85,000, say their school will remain open on Saturday and Sunday, with crisis counsellors available.