Three Canadians are dead and four others injured after a drunk driver fell asleep at the wheel of his tractor-trailer and smashed in a bus full of tourists in rural Mexico.

At least 11 people died in the accident, including eight Americans.

The bus was transporting a tour group, mostly made up of Americans and Canadians, from McAllen, Tex., to Zacatecas, when it was hit by a transport truck.

Coahuila state police said 26 people were on the bus, and that they were mostly retirees.

Police said the truck driver appears to have fallen asleep and smashed into the oncoming bus, slicing it open along one side.

The Canadian Press has identified the Canadians killed as: 56-year-old Robert Lacas from Quebec City, Carolyn Kowaleski, 68, of Caledonia, Ont. and Marilyn Jackson, 67, of Vancouver.

Lacas's wife, Line Carrier, was one of four Canadians believed to be injured and taken to hospital.

Carrier's son, Christian Poulin, said the couple was on a six-month working holiday in Mexico.

The two left their home in October and had left their car in a campground in McAllen last weekend before boarding the bus for their Mexican trip.

"They were a couple that loved each other and still had a sparkle in their eyes when they looked at each other," Poulin told CP.

"They raised their family, worked hard and were thinking about themselves -- and it was time to do that -- and sadly misfortune has befallen them."

According to Poulin, no one at the hospital where Carrier is being treated speaks English or French. Relatives are attempting to secure a translator for her, he said.

One of Lacas's co-workers, Jean-Luc Morin, said the couple had set aside six months to travel through the southern United States.

They were due back in Quebec at the end of April so Lacas could speak at a conference, Morin told CP.

Lacas worked at the Quebec Centre for Industrial Research for 20 years before starting his own consulting company in 2002, CP reported.

Carrier retired last September.

A 67-year-old woman from Vancouver was also reported to have been killed in the accident.

The crash occurred about 50 kilometres outside of Saltillo, the capital of Coahuila state.

Polo Sandoval, a reporter from KRGV TV in Rio Grande Valley, Tex., said that Coahuila State Police believe the driver of the tractor trailer was under the influence of either drugs or alcohol at the time of the accident.

"There are preliminary indications that show that he was under the influence of either drugs or alcohol and he veered off the road there near Monterrey, Mexico, about three hours south of the (U.S.) border," Sandoval told CTV Newsnet during an interview on Tuesday afternoon. "And then in his attempt to gain control of the tractor trailer he over-corrected himself and unfortunately that took him right into traffic and into the oncoming path of the bus."

Sandoval said that 15 injured passengers, as well as the truck driver and one of the bus drivers, have been taken to three local hospitals.

Foreign Affairs has still not confirmed that Canadians were among the dead and a spokesperson confirmed few details about the incident earlier Tuesday.

"We are aware that Canadian citizens were involved in the accident and are providing consular assistance as required," Alain Cacchione told CTV.ca.

"No further information can be provided at this time."

According to newspaper reports, the dead passengers included four children, as well as the bus driver, who was identified as Cesar Garcia Huerta.