Fifteen people, most of them children, were being kept in hospital overnight after a hay wagon overturned Wednesday afternoon on the outskirts of Sherbrooke, Que.

"Three people are still in intensive care, but their injuries are not life-threatening, even though they are serious," said Jacinthe Ouellette, a spokeswoman for Sherbrooke's University Hospital.

Injuries ranged from scratches to broken bones.

The children, aged six to 12, were on an outing organized by a Christian day camp, CBC's Catherine Cullen reported. The children were reportedly from Quebec, Ontario and the U.S.

They were riding on the open trailer when it toppled over Wednesday afternoon in a field by Giroux Road, in Bromptonville.

A dozen ambulances and six fire trucks were dispatched. They arrived to find a "chaotic" scene, said Sherbrooke Fire Department Chief Stéphane Simoneau.

The children were afraid and screaming, Simoneau said in an interview with Radio-Canada.

Police said 53 people were involved in the accident, including the driver.

Twenty-six people were injured and taken to hospital by ambulance, police said. The remaining 27 were also taken to hospital by bus, just to be checked out.

Hospital administrators had to recall four doctors who were on holiday because of the number of victims needing simultaneous care.