RALPH, Sask. - People in a rural area of southeast Saskatchewan were told to evacuate Monday when rail cars caught fire following a crash involving three Canadian Pacific Railway trains, some carrying dangerous goods.

Railway officials said the train cars on fire were empty but contained residue of a regulated commodity called vinyl acetate, a substance used in the manufacture of household and wood glue. Up to 14 cars in total derailed.

"We're not going to risk life or limb to go in there and try to do anything,'' Denis Pilon, the fire chief in nearby Weyburn, told CTV Regina. "We're going to let it burn out.''

The accident forced the closure of the rail line and Highway 39 near the tiny farming community of Ralph, about 150 kilometres southeast of Regina.

Thick, black smoke and flames poured from at least two train cars as fire, police and hazardous materials crews responded to the scene. The smoke could be seen from 50 kilometres away.

"At approximately 8:15 a.m., a southbound Canadian Pacific train made contact with a second train, which was stationary. There was a third train sitting adjacent on the siding,'' said CP spokesman Mike LoVecchio.

"There are two cars on fire that I know of. There were no injuries and no threats to people in the surrounding area.''

Pilon put it succinctly: "Three trains were passing each other and one misjudged and drove up the back end of another train.''

One train car near the burning cars was carrying glycol. Another had been carrying butane, but was empty at the time of the crash, he said.

RCMP reported that some of the cars contained di-nitrogen tetroxid and nitric oxide.

People living within 1 1/2 kilometres of the area were asked to leave as a precaution. CTV reported that 12 families in all were affected.

LoVecchio said CPR would begin investigating once the fire was out.

There was no immediate information on how many cars in total made up the three trains.

"The critical thing here is that public safety is protected,'' he said. "We are looking after the residents who have been affected.''

Di-nitrogen tetroxid can burn eyes, lungs and skin. Nitric oxide can also be corrosive.

Area resident Connie Dorsch was relieved not to have to leave her farm.

"There was a very small chance that we would have to evacuate,'' she said. "(We were told) it was not dangerous to humans or animals unless you were right there.''

CPR officials flew in by jet from across western Canada and U.S. to look at the site and "make sure that our people and the public are safe,'' said spokesman Ash Olesen.

"(We will) determine if there's been any impact to the environment, conduct an investigation with respect to cause and then begin to contemplate restoration of our rail activity.''