American safety regulators are issuing a warning about shipping oil produced in North Dakota and Montana by rail.
That's the same oil involved in the Lac Megantic disaster, and in the big fire outside Casselton North Dakota on Monday.
Officials say the oil produced in the Bakken region is more flammable - and therefore more dangerous - than that produced elsewhere.
The warning comes as record volumes of crude oil travel by rail across Canada and the US.
Federal regulators have been studying the issue for the past four months, in the aftermath of the Lac Megantic inferno.
Three other derailments involving crude have occured in the last six months.
North Dakota is the second biggest oil producer in the US, behind Texas.
Its jump in production is attributed to an increase in hydraulic fracturing, or fracking.
Supporters of the proposed Keystone XL Canada-US pipeline are saying its construction will reduce the likelihood of accidents involving oil-carrying trains.
But its opponents say pipelines offer no safety guarantees either, pointing to several big spills, including one in September that saw 20,000 barrels on crude leak in North Dakota.