The images were strikingly familiar: A dark stretch of rural Saskatchewan land, a fiery blaze and thick smoke billowing from train cars gone topsy-turvy.

"Another train by Guernsey!!" read the tag on one social media post.

Thursday's early-morning train derailment two kilometres east of Guernsey, Sask., was the second Canadian Pacific Railway crude oil crash to happen near the small hamlet in less than two months.

The first occurred on Dec. 9, 2019, just after midnight. A Canadian Pacific Railway train hauling oil derailed west of Guernsey. At least 19 of its train cars leaked an estimated 1.5 million litres of crude — more than six times the amount of product that poured into the North Saskatchewan River from a Husky Energy pipeline in July 2016.

Drone footage of the second derailment on Thursday clearly showed at least two large pools of black sludge staining the snow-covered ground alongside Highway 16. Thirty-one of the train's 104 cars derailed.

But no estimate of the latest spill has been released yet. The Transportation Safety Board deployed two investigators to the site on Thursday, but firefighters were still battling the blaze as of early Thursday afternoon, according to the Saskatchewan Public Safety Agency (SPSA).

Still, the clustering of two similar incidents only a few kilometres apart on the rail line's Sutherland subdivision quickly drew notice and alarm.

Wow just a couple of months ago another one happened!! <a href="https://t.co/ycZW6jHrvB">https://t.co/ycZW6jHrvB</a> —@ElaineS41103933

"It is a concern that two derailments happened in that vicinity, absolutely," said Marlo Pritchard, the president of SPSA.

Federal Transport Canada Marc Garneau simultaneously ordered that all large trains carrying dangerous goods on federal rail lines slow down their speeds — even as the speed of Thursday's crashed train remained unclear.

December's train was travelling about 72 km/h, which is the maximum speed on that section of the subdivision, according to the TSB.

Garneau's countrywide order called for trains going through metropolitan areas like Saskatoon to cap their speed at 32 km/h.

The train was headed eastbound toward Guernsey, according to information shared with the Transportation Safety Board of Canada by CP. (CP Rail)

On tracks everywhere else — including the portion of the Sutherland subdivision near Guernsey — trains can now only travel up to 40 km/h — a nearly 50 per cent reduction in maximum speed for that area.

"I am very concerned about the derailments of railway cars containing dangerous goods in the past 12 months," Garneau said of his 30-day order.

In its own statement Thursday afternoon, CP said it had already slowed down its trains but fully supported Garneau's directive.

"Until we better understand the facts relating to today's incident, it is prudent to operate with an abundance of caution," CP president and CEO Keith Creel said in the statement.

During a Thursday press conference held by the Saskatchewan Public Safety Agency, Pritchard was asked if all train activity on the Sutherland subdivision ought to be halted until the TSB's latest investigation wraps.

"It's way too early to even talk about that," Pritchard said. "We have to wait to see what the cause is because it might not have anything to do with the one that happened before [in December]."

"It is a concern that two derailments happened in that vicinity, absolutely," said Marlo Pritchard, president of the Saskatchewan Public Safety Agency. (CBC)

According to the TSB's first update on the December derailment, "initial site examination determined that the covered hopper car in position two and the following 33 tank cars had derailed."

Ian Naish, a former director of rail investigations for the TSB, said that could point to one potential factor.

"Usually when there's a derailment and the first car off is just behind the locomotive, something like three times out of four that's because of a broken rail," he said. "It's highly likely it's a broken rail."

John Herbert, the director of communications for the U.S. Railway Supply Institute (RSI), declined to comment on Thursday's derailment, saying the organization was waiting for more information to come out.

But he shared an RSI table showing crude oil derailments in North America since 2006. Several were caused by broken rails.

Eight of the crude oil derailments listed in this document were caused by a broken rail. (Railway Supply Institute)

Testing and inspections could reveal if there's something wrong with the track, Naish said.

Melanie Loessl, whose home was near the site of the December derailment, said CP had done some work on the track throughout 2019 and as recently as a week or so ago. CBC has asked CP what work was done and why.

"I have nightmares of it happening here again," Loessl said Thursday.

CP has asked to test Loessl's water, she said.

The company has said neither derailment affected waterways.

'Why did those two trains derail?'

In addition to the speed of the train, another factor that remains unclear about Thursday's derailment is which types of tank cars the train was hauling.

December's CP train was carrying a mix of jacketed CPC-1232 cars and TC-117R cars, CP previously confirmed.

TC-117R cars are retrofitted to meet the same standards as brand new, Transport Canada-endorsed TC-117s. The new TC-117s are meant to be less prone to rupturing during crashes in the wake of the Lac-Mégantic, Que., rail disaster.

A diagram of the new TC-117 tank type endorsed by Transport Canada. (Transport Canada/CBC)

But a major rail carrier of crude oil in the United States has reportedly cracked down on the retrofitted 117R tank type following a June 2018 derailment in Iowa that leaked 870,645 litres of oil into a waterway.

The shells on retrofitted 117R cars are slightly thinner than those on new 117 cars: 7/16th of an inch thick, versus 9/16th of an inch thick, according to Naish. CBC has asked CP what type of tank cars were on Thursday's train.

Regardless of which type of tank Thursday's train was pulling, "the tank cars don't seem to be able to contain anything and they do pile up and there's big releases," Naish said.

Thirty-one of the train's 104 cars derailed Thursday. Twelve were still on fire as of early afternoon. (Submitted by Philippe Gaudet)

Jean-Pierre Gagnon, a retired Transport Canada engineer, said the tank type must ultimately take a backseat to what caused Thursday's crash, however.

"The damage or hazard from crude oil is secondary to the main issue, which is the derailment," he said. "If you don't derail the train, then there's no crude oil problem.

"So why did those two trains derail? What's the cause?"

The TSB has said the two derailments will remain separate investigations for now.

Naish said he's never before seen two crashes by the same company, in the same area, in such a small period of time.

"Is it a coincidence," he said, "or is it a systemic deeper problem?"