Cleanup crews work along the banks of West Barneys River on Thursday. (CBC)Ralph Michael Coady, 60, of Frasers Mountain, N.S., and Christopher Walsh, 37, of Smith's Creek, N.B., were the drivers killed in a collision on the Trans-Canada Highway in northern Nova Scotia Wednesday that set off a fire and spilled oil into a nearby river.

The RCMP are investigating the head-on collision, which occurred around noon Wednesday near Kenzieville, N.S., between a tanker truck driven by Walsh and a pickup truck driven by Coady.

The crash killed both drivers and sent the tanker tumbling off a busy section of the highway.

The tanker, owned by Newalta Corp., an industrial waste management firm, was carrying 38,000 litres of used oil, some of which spilled into West Barneys River.

Thick black smoke from the burning oil billowed above the crash scene for hours after the accident and could be seen from several kilometres away.

Cleanup crews have been at work since Thursday along the banks of the river, using containment booms and absorbent pads to clean up the oil.

Firefighters said Wednesday they would let a fire from the collision burn through the night. (CBC)Excavators were also removing some contaminated soil from the area, and several trucks at different locations were vacuuming oil from the river, said Kim Bard, a spokeswoman for the provincial Environment Department.

Bard was unable to provide an estimate of how much oil ended up in the river.

Fresh water was delivered to an aquaculture hatchery about 4.5 kilometres downstream, where 500,000 rainbow trout had been loaded on the day of the accident.

Chuck Brown, who works with the company that owns the fish, said the amount of feed given to the fish has been cut back because of the restrictions on fresh water.

"By cutting back on their feed, it just cuts back on their activity in general," he said. "They're using less energy. They're conserving energy, and that's what we really need them to do at this point."

The polluted section of the river is no longer feeding the pond, and Brown said officials have told him it could take weeks until the farm is able to access fresh water from the river again.