Forty-three schoolchildren from Rugby needed medical treatment today after suffering suspected exhaust poisoning.
The children, from Harris School in Rugby Warwickshire, suffered breathing problems, nausea and vomiting after inhaling dangerous fumes on board their bus while travelling into school this morning.
A total of 24 were taken to Walsgrave Hospital in Coventry and a further 16 suffered breathing difficulties and were treated by ambulance crews at the school. Eight others suffered minor symptoms.
They are believed to have become ill after breathing in diesel fumes when their Stagecoach bus broke down. They remained aboard the faulty bus for 40 minutes while waiting for a replacement.
It was only when they got to their school, on Overslade Lane in Rugby, that the pupils, who are aged between 11 and 16, developed their symptoms.
A spokesman for Stagecoach, which runs the bus service, said checks have begun to see whether the exhaust system was damaged by an object while en route.
"Our first thoughts are for the welfare of the children who were on board the bus," he said. "We are already working closely with the police and other authorities as part of the investigation into the incident."
By 2.30pm all children taken to hospital had been released.