A collision west of Waterloo, Ont., has killed 11 people — including migrant workers — in what one veteran police officer described as the worst crash he has seen in nearly 30 years on the job.

The crash happened in the hamlet of Hampstead shortly before 5 p.m. ET when a flatbed truck collided with a van at Perth County Road 107 and Line 47, about 20 kilometres northeast of Stratford, Ont.

Ten people in the van were killed as well as the driver of the truck, making it the worst crash in the province in at least a decade.

One survivor was airlifted to hospital in Hamilton with life-threatening injuries, while two others were being treated for serious injuries in Stratford.

"I've been on the job for 28 years and I've never seen anything quite like this collision tonight," OPP Insp. Steve Porter said at news conference near the site of the crash Monday evening.

He said a number of "critical incident stress people" were at the scene to help emergency workers cope with the horrific nature of the crash.

The crash propelled the van between 20 and 30 metres from the intersection, CBC's Steven D'Souza reported.

Elizabeth Cooper, an editor with ionStratford.ca who was at the site of the crash, said the truck had flipped over onto its roof. She described the passenger van as "almost unrecognizable," lying against a farmhouse near the intersection.

Cooper said there was no snow in the area and the sky was clear, suggesting that visibility was good at the time of the crash.

Police were told the van was carrying a group of migrant workers, Porter said, but there were no details on where they were from. There are reports the crew had just left a nearby poultry farm.

A number of the victims spoke Spanish, D'Souza said, which made it difficult for emergency workers to communicate with them.

The van had been travelling westbound on Line 47, which is controlled by a stop sign at the intersection, when it collided with a southbound transport truck, Porter said.

Investigators believe driver error was behind the crash, OPP Sgt. David Rektor said, but offered no other details.

Jared Martin, chief executive of Speedy Transport, released a statement saying one of its truck drivers was killed in the crash but he did not release the driver's name.

"Our thoughts and prayers are with our driver’s family and the families of the other victims involved in this horrible tragedy," Martin said.

"This is the first fatality we’ve experienced on the road since inception," he said.

Collision at stop sign

Martin said he was told by provincial police that the van failed to stop at the stop sign and was hit by the Speedy Transport vehicle.

Police said they believe 13 people were in the van, which had a capacity of up to 15 passengers.

Premier Dalton McGuinty gave his sympathies late Monday night.

"On behalf of 13 million Ontarians, I want to offer our deepest condolences to those who lost a loved one and to offer our most sincere prayers for those taken to hospital," said McGuinty, who thanked emergency workers and investigators who responded to the collision.

The United Food and Commercial Workers Union also offered its condolences to the families of the victims and called for a thorough probe into the cause of the crash.

"The safe transportation of agriculture workers has always been a critical issue, and we must expect a relentless investigation into how and why such a tragedy occurred," said UFCW president Wayne Hanley in a statement.

The UFCW noted that more than 20,000 migrants work in the Ontario agriculture sector each season.

The crash occurred about 20 kilometres northeast of Stratford, Ont. (Google) With files from The Canadian Press