* Westbound CN Rail train derails near Edmonton
* One car of liquid petroleum gas explodes, three on fire
* No injuries, but critics warn of crude-by-rail risks
By Nia Williams and Solarina Ho
CALGARY, Oct 19 (Reuters) - A train carrying crude oil and liquefied petroleum gas derailed west of Edmonton, Alberta, on Saturday, causing an explosion and fire but no injuries, Canadian National Railway said on Saturday.
One rail car carrying liquefied petroleum gas on the westbound train exploded and three others also caught fire. Emergency crews battled the flames and worked to prevent the burning cars from triggering more explosions, a municipal authority spokesman said.
Residents were evacuated from Gainford, Alberta, 85 km (53 miles) from the provincial capital Edmonton, after the accident, which highlighted concerns in Canada about moving oil by rail. The community, part of the municipality of Parkland County, has a population of just over 100 people.
"We have cars on fire right now and there was an explosion earlier this morning. The major priority right now for our guys out in the field is containing these fires," said Parkland County spokesman Carson Mills.
It is the third Canadian National Railway derailment in recent weeks and is likely to fan opposition to the crude-by-rail boom taking place in Canada as the country's oil producers seek alternatives to congested pipelines.
Rail safety has become a central issue in Canada since the incident in Lac-Megantic, Quebec, in July, when a runaway train carrying crude products exploded in the center of the town, killing 47 people.
CN Rail said 13 cars had derailed in the accident in Alberta, which happened at around 1 a.m. There were no injuries, but local authorities evacuated the area as a precaution, CN spokesman Louis-Antoine Paquin said in an email.
Nine of the derailed cars were carrying liquefied petroleum gas and four carried crude. The crude oil cars were intact and kept away from the fires with no indications of any leaks.
Mills said 49 people had registered at the emergency evacuation center and would not be allowed to return home for at least 24 hours.
The main east-west highway traversing central Alberta was closed for at least 24 hours.
Canada's Transportation Safety Board said it has sent a team of investigators to the site.
The derailment near Gainford comes days after a CN train carrying anhydrous ammonia derailed in Sexsmith, Alberta, earlier this week.
A CN freight train derailed near the town of Landis, in the western Canadian province of Saskatchewan, on Sept. 25, sending 17 cars off the track, one of which leaked lube oil.
On Thursday, the Canadian government imposed new regulations requiring tests to be conducted on crude oil before transporting or importing it into Canada. In the Lac-Megantic crash, inspectors determined that the oil the train carried was more explosive than labeled.
Canadian Transport Minister Lisa Raitt said the new measure, to enhance the safety of dangerous goods, would require "any person who imports or transports crude oil to conduct classification tests on crude oil."
Weekly figures from the Association of American Railroads, which do not distinguish between shipments of refined fuel and crude oil, showed 6,937 rail cars were loaded with petroleum and petroleum products in Canada in the week ended Oct. 12, up 13 percent from the same week in 2012. That is roughly equivalent to 594,600 barrels per day.
The growth shows no sign of slowing, with around 550,000 barrels per day of dedicated crude-by-rail terminals due to be operational in Western Canada by the end of 2014.
Critics say the rush to use rail to transport crude and sidestep pipeline bottlenecks means that safety is being overlooked, raising the risk of more derailments.
"This is becoming the new normal as we have movements of crude-by-rail skyrocketing at a time when the safety standards have not kept up," said Keith Stewart, climate and energy campaign coordinator at Greenpeace.
"We have train cars which were never designed for dealing with these kind of hazardous and explosive products," he said.
It was not immediately clear what type of rail cars were involved in the latest incident, but past concern has centred on the older DOT111 tanker cars such as the ones involved in the Lac-Megantic crash, which lack twin hulls or extra strengthening.
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