(Adds details, commuter train information)
TORONTO, Feb 24 (Reuters) - Passenger and freight train service across southern Ontario started to resume on Friday after being halted due to a power outage at Canadian National Railway's rail traffic control center, officials said.
Scott Money, a spokesperson for Metrolinx, the region's public commuter service operator, said a network-wide outage lasting about two hours affected upwards of 5,000 passengers.
CN spokesman Patrick Waldron said some trains had begun moving again by mid-morning. He could not say how many were still halted but expected full service to be restored by the end of the day.
"CN personnel are working to restore full service and systems as quickly and as safely as possible," he said.
"This is impacting freight service across the province."
The domino effect could slow national freight routes as outages at a traffic control centre could mean signals turn red throughout the line, said Fred Frailey, a writer for Trains magazine who has covered the industry for more than 30 years.
"If you lose your signals, you're just on your hands and knees," Frailey said.
CN runs seven to nine freight trains daily between Montreal and Toronto and between Toronto and Winnipeg, Frailey said, carrying items such as retail goods, auto parts, crude oil and lumber. (Reporting by Solarina Ho; Editing by James Dalgleish)