Police and EMS workers who were on the scene after a collision that killed 10 migrant workers and one truck driver said Tuesday it was "amazing" and a "miracle" that three people survived.

A flatbed truck and a 2007 GMC Savanna passenger van collided shortly before 5 p.m. Monday northeast of Stratford, Ont., police said.

The van required a Class F licence because it had more than 10 seats. The OPP says they have yet to determine the driver of the vehicle.

Ontario's transportation minister appealed for patience while police investigate.

"It's not a clear-cut accident, obviously, with one stop sign and one through street," Bob Chiarelli told reporters Tuesday. "So we need to look at the facts."

"It is so serious, it is so severe and it is so sad really that this thing can still happen, that we've got to be so comprehensive that we do everything possible to ensure that it never happens again."

The workers, all who were from Peru, had been working at a nearby poultry farm vaccinating chickens.

Poultry farmer Albert Burgers said he was shocked to find out many of his workers were the victims of Monday's crash.

He said some of the group of 16 migrant workers -- who were contracted through another business – were people he's seen for years, while others were new to him.

He said he 13 drove off in one van, while three left in a second van. He recalls them as being happy and in a good mood after they left his farm yesterday. The accident happened not long after they left.

During a news conference on Tuesday, OPP Const. Kees Wijnands said it was incredible that anyone had survived.

"All we know is that the persons are all still alive which is a great thing...and that's very amazing considering the crash and the carnage," Wijnands said, adding that the accident was among the worst he has seen in 25 years of policing.

Linda Rockwood, director of Perth County EMS, said five of the passengers were already dead when paramedics arrived, and the others died on the scene.

Of the three survivors, Rockwood said one was airlifted to Hamilton and two were taken to Stratford General Hospital -- though one of those was later transported to London for further treatment.

"From the reports I got back from my staff I believe yes, it was a miracle," Rockwood told reporters.

"There was carnage and there were a lot of people in that minivan and firefighters were pulling them out one after another and one would come and then another would come and so it was really difficult for staff."

Transport Canada is investigating the incident but says it cannot comment on the matter until its investigation is complete.

Ontario Health Minister Deb Matthews says the government is investigating whether the survivors are covered under the province's health plan.

Matthews says seasonal migrant workers are covered during their time in the province, assuming all the proper procedures are followed.

Immigration Minister Jason Kenney offered his condolences to the victims' families during a scrum in Ottawa.

Police have released few details about the migrant workers who were killed in the crash. Ian Forrest, mayor of Perth East, said a fund has been set up with CIBC to accept donations on behalf of the families, some of whom he said live in Canada, while some live in South America.

Cheryl Legate, executive director of Victim Services for Perth County, said the agency is attempting to get in touch with those relatives.

"It's a big community and there are lots of family and friends around," Legate told reporters.

"We don't know the extent of the effect on the community at this point and on families in Peru. Certainly some of them will have family out of country and some have families in the area and details of that are unfolding."

There are reports that some of the victims had only recently arrived in Canada, but officials said Tuesday some had been living here for years.

Police are not releasing the identities of the victims or the survivors until their next-of-kin have been notified.

The van was travelling west on Line 47 when it was T-boned by a flatbed truck that was heading south on Perth Road 107, in the rural hamlet of Hampstead.

Witnesses said the truck, operated by Speedy Transport, collided with the van at about 5 p.m. ET.

The impact of the crash slammed the van into the side of a nearby house.

"I've been on the job for 28 years and I've never seen anything quite like this collision tonight," OPP Insp. Steve Porter told reporters on the scene Monday night.

At least some of the workers were wearing their seatbelts and firefighters had to cut them off as they scrambled to free the victims.

Police said it's not clear whether the van obeyed a stop sign at the intersection. They are not ruling out any possible crash causes, including speed and alcohol.

The speed limit on that stretch of Perth Road 107 is 80 kilometres an hour. The weather was good and the roads were clear at the time of the crash.