The minivan rolled on Highway 20, east of Quebec City, on Monday afternoon. ((Google Maps))

A minivan carrying migrant agriculture workers rolled over and threw some onto Highway 20 east of Quebec City on Monday, killing one and injuring seven others.

The van flipped after the driver lost control east of Montmagny on the south shore of the St. Lawrence on Monday afternoon, Quebec police said.

Three passengers were thrown out of the van.

"We think the driver had a medical problem or condition, or fell asleep," said Ann Mathieu, a spokeswoman for the provincial police, the Sûreté du Québec.

Three people are in serious condition.

The workers only speak Spanish, so police had called in an interpreter to help with the investigation.