The oil-carrying Canadian Pacific Railway train that derailed and lit up an area of rural Saskatchewan earlier this week was pulling modified tank cars meant to reduce the risk of puncturing and other damage during a crash.

The train derailed west of Guernsey, Sask., just south of Highway 16 shortly after midnight on Monday. Thirty-four cars came off the tracks, according to CP. No one was injured.

CP does not own any of the rail cars involved in the incident, according to CP spokesperson Andy Cummings.

Cummings confirmed the train's cars were a mix of retrofitted TC-117 cars and jacketed CPC-1232 cars, both of which "meet all Transport Canada standards."

Both tank types are also considered improvements over the DOT-111A steel cars involved in the July 2013 Lac-Mégantic, Que., train derailment that killed 47 people.

The Transportation Safety Board of Canada had called for the removal of the thinner-hulled 111A tanker cars for more than 20 years, underlining their vulnerability in case of a crash.

After the Lac-Mégantic crash, the federal government unveiled the rail cars it hoped would become the new standard for transporting flammable liquids.

Dubbed the TC-117 in Canada (DOT-117 in the U.S.), these cars have better thermal protection and are supposed to withstand puncture and other damage better than their predecessors, according to Transport Canada.

(Transport Canada/CBC)

"Thermal protection increases the survivability of tank cars in the event of a fire," reads a TC-117 info sheet on the Transport Canada website.

"The thermal protection required for the TC-117 must be able to withstand exposure to a 100-minute pool fire and a 30-minute jet fuel fire without rupturing."

The jacketed 1232 cars that were also on the CP train are made of tougher material than the rail cars that exploded in Lac-Mégantic. According to the U.S. Bureau of Transportation Statistics, 1232 cars are meant "to be safer than DOT-111 tank cars for carrying petroleum crude oil and ethanol."

Given that a mix of 1232 and 117 rail cars were in Monday's car pile, "the TSB would probably examine if there were any differences in crash performance between the two types," said Ian Naish, a rail safety consultant and former Transportation Safety Board of Canada investigator.

The Saskatchewan Public Safety Agency said it did not know whether Monday's crash was the largest in the province's history in terms of the number of derailed cars. (Don Somers/CBC)

Signs of leakage

Both a fire chief who responded to the derailment near Guernsey and a woman who lives right near the crash site said they saw signs of leakage from the tanks.

"I saw some of [the tanks] had oil on the outside of them. It looked like that had burned," said resident Melanie Loessl.

"There were large pools of crude that were laying in the ditch," echoed Humboldt fire Chief Mike Kwasnica.

It's not clear how much oil leaked and how much soil was contaminated. The Saskatchewan government said the derailment site covered five to 10 acres.

The Saskatchewan NDP party is calling for a full review of the derailment's environmental impacts.

"We're obviously deeply concerned about the safety of rail workers and first responders, and the risk of land and water contamination after this terrible accident," said NDP finance critic Trent Wotherspoon.

CP has already said there is no impact to waterways.

The Saskatchewan Ministry of Environment said in a statement that an environmental assessment is "a normal course of business in these types of situations."

"The Ministry of Environment works with the responsible party, in this case Canadian Pacific Railway, and oversees the environmental assessment and remediation efforts, which are already underway," the statement reads.

"Canadian Pacific Railway is responsible for all costs associated with the derailment, including the emergency response, environmental assessment and remediation efforts."

Marlo Pritchard, the president of the Saskatchewan Public Safety Agency, said at a press conference Tuesday that he did not know whether Monday's crash was the largest in the province's history in terms of the number of derailed cars.

The train derailed west of Guernsey, Sask., just south of Highway 16 shortly after midnight on Monday. Thirty-four cars came off the tracks, according to CP. (CBC News)

The TSB investigation

Investigators from the TSB began probing the cause of the crash mid-Tuesday, once firefighters had contained the worst of the fires.

Naish said crashes typically involve more than one cause and that investigators will look at a host of factors, including the train's maintenance record, the condition of the track, how rested the crew was and the speed of the train.

"The faster you go, if there is a pile-up, the worse the outcome," he said.

Tank cars will likely be sent to TSB engineers for analysis, Naish said.

If any operational issues are found, Transport Canada will be notified, Naish added.