TORONTO — A Canadian National Railway Co. train holding cargo that included gas and crude oil was burning for a fourth day in New Brunswick on Friday as crews worked to remove the last derailed freight cars adjacent to the fire.

A total of 19 cars and one locomotive on the 122-car, four-locomotive train went off the rails on Tuesday evening, just a week after another fiery derailment of a crude oil train in North Dakota.

“Once [the car removal] is completed, the plan is to address the fire involving two derailed LPG (liquid petroleum gas) tank cars and one crude oil tank car later today,” CN Rail spokesman Mark Hallman said on Friday.

Hallman said CN hopes to extinguish the fire as quickly as possible to allow evacuated residents around the nearby village of Plaster Rock, New Brunswick, to return home, but offered no timetable.

Officials were still investigating the nature of the damage to all the train’s tank cars and the volume of product affected, he added.

Calls for tougher regulatory measures in the United States and Canada have intensified after a string of high-profile rail accidents involving dangerous goods, including a disaster last summer in Lac-Megantic, Quebec, that killed 47 people. A rise in shale oil production has spurred a huge boom across the continent in shipping crude via rail.

Recent derailments have included older tank-car models that regulators have deemed faulty and vulnerable to punctures. It is unclear whether the crude tanker that was still burning in New Brunswick was the older DOT-111 model or a newer model that complies with stricter voluntary standards for tankers adopted in October 2011.

“The older DOT-111 tank cars comply with current regulatory requirements, so CN, under its common carrier obligations, is obliged to transport them,” Hallman said, but he reiterated CN’s support for calls to improve tank car safety.

Several U.S. lawmakers urged swift measures from Transportation Secretary Anthony Foxx, who in turn promised that tougher federal standards for tank cars would come “in weeks, not months,” according to North Dakota Republican Sen. John Hoeven.

Canadian Transport Minister Lisa Raitt is working closely with Foxx and other U.S. officials on standards for the DOT-111 tankers, a spokeswoman for Raitt said late on Thursday.

CN’s Hallman said that tank car owners — generally shippers and rolling-stock leasing companies — should pay for costs of retrofitting tankers. Energy groups are opposed to the tanker proposals because they say the cost of retrofitting roughly 80,000 cars could be prohibitive.