(Adds details and comment beginning in third paragraph)
CALGARY, Alberta, Feb 18 (Reuters) - Canadian National Railway Co said on Wednesday its shipping customers should expect delays as traffic on its mainline returns to normal after a weekend derailment of a train carrying crude oil.
The derailment site 80 kilometers (50 miles) south of Timmins, Ontario, was cleared at 10:30 p.m. local time on Tuesday. The accident blocked traffic on the railway's main east-west track between Montreal and Winnipeg, Manitoba, the company said.
Late Saturday night, 29 cars carrying Alberta oil sands crude to eastern Ontario derailed and seven caught fire. Two of the cars were still burning. Patrick Waldron, a CN spokesman, said the fire was under control and the cars are a safe distance from the tracks.
"Trains have resumed running through the derailment area at a reduced speed due to the ongoing clean-up work at the site," he said in an email.
Waldron said he "cannot characterize or speculate on a timeline ... for when traffic would return to normal at the site or for the company's system overall."
The company is working with regulators to complete the remediation work at the remote site.
CN Rail said the derailed cars were CPC 1232 tanker cars, which are supposed to be safer than the older DOT-111 crude tankers that derailed and burned in downtown Lac Megantic, Quebec, in July, 2013, killing 47 people.
The older DOT-111 cars have been criticized for being prone to puncture in accidents.
A derailment on Monday of a CSX Corp oil train in West Virginia that caused 20 cars to catch fire also involved CPC 1232 tankers rather than the older version. (Reporting by Scott Haggett; Editing by Jeffrey Benkoe)