(Adds railway comments on number of cars involved in derailment)

By Jeffrey Hodgson

TORONTO, March 8 (Reuters) - A Canadian National Railway Co train carrying crude oil that derailed near the northern Ontario community of Gogama early on Saturday is still on fire, the company said late on Sunday.

The derailment is CN's second in the region in just three days and the third in less than a month. It was the latest in a series of North American derailments involving trains hauling crude oil, raising concerns about rail safety.

"Fire suppression activities are beginning, as is construction of the track diversion," CN spokesman Mark Hallman said in an email, adding that responders were working in shifts around the clock.

The railway said it confirmed that 38 cars were involved in the derailment. The train had 94 cars containing crude oil. CN did not yet have a definitive count of the number of cars that had caught fire.

The railway did not estimate when the fire will be extinguished and the line reopened.

The Ontario Provincial Police said earlier on Sunday on Twitter that the fire was burning at 80 percent of full size and posted a photo from the morning showing thick clouds of black smoke still coming from the site.

Hallman said air quality monitoring has indicated no air issues at either Gogama or a nearby aboriginal community.

The police force reopened a nearby highway closed after the derailment, but warned there would be delays for residents as CN moves equipment.

The railway said on Saturday that a bridge over a waterway had been damaged and that five tank cars had landed in the water. Oil had leaked into the water and booms were deployed to try to contain it.

CN said the crude oil on the train originated in Alberta and was destined for eastern Canada.

The incident comes after another derailment, on Thursday, blocked CN's main line in northern Ontario.

CN said the latest derailment occurred 2 miles (3.2 km) northwest of Gogama, which is some 373 miles (600 km) north of Toronto. It occurred just before 3 a.m. (0800 GMT) on Saturday and is affecting rail traffic running between Toronto and Winnipeg, Manitoba.

The Transportation Safety Board of Canada, which is investigating, noted on Saturday that the accident occurred about 23 miles (37 km) from the site of a Feb. 14 accident involving a CN crude oil train. (Editing by Leslie Adler and Chris Reese)