LONDON (AP) — A bus carrying middle school children overturned and slid on its roof down a steep embankment in southwest England on Thursday, killing one student and seriously injuring two, authorities said.

Three helicopters and 20 ambulances dispatched to the crash took 21 people to the hospital and crews treated others at the scene, said Wayne Darch, deputy director of operations for the South Western Ambulance Service.

Prime Minister Keir Starmer said his thoughts were with the family and friends of those involved in the heartbreaking crash.

“There are no adequate words to acknowledge the death of a child,” Starmer said on X. “Thank you to the emergency workers who are responding at pace.”

An off-duty firefighter who was driving behind the bus was at the scene almost immediately and began freeing passengers while dozens of other firefighters and ambulance crews were dispatched, said Gavin Ellis, chief of Devon and Somerset Fire & Rescue Service.

“Our crews carried out a number of extrications and rescues in extremely difficult circumstances, and they also supported our ambulance colleagues with casualty treatment,” Ellis said.

The bus carrying 60 to 70 passengers was returning to Minehead Middle School in Somerset from a day trip when it crashed just before 3 p.m., police said.

The school, which teaches children from ages 9 to 14, was in its final days before summer break.