(Montreal) The massive breakdown on Canadian National Railway (CN) lines that delayed thousands of commuter train users in the Toronto, Ontario area during the rush hour evening Tuesday, can be attributed to a software upgrade, according to the company.

“At this time, our teams have determined that the outage was caused by an internal systems upgrade, which affected CN’s ability to connect to the internet,” said Jonathan Abecassis, CN spokesperson , during an interview.

“There is no indication that this is a cybersecurity incident. At no time was public safety compromised, and at no time was data affected. »

The digital outage “prevented CN from connecting to the internet,” he said. It also blocked regional transit authority Metrolinx and its GO Transit trains from connecting to CN servers, which is essential for digital communications that tell locomotives where to move, Abecassis said. GO Transit trains run partly on CN-owned tracks.

Earlier, the computer malfunction forced Go Transit trains — the public transit network in the Greater Toronto and Hamilton Area — to stop at the nearest station. Meanwhile, commuters flocked to Toronto’s Union Station during rush hour in hopes that the system would restart.

The UP Express, which runs from downtown to Toronto Pearson Airport, also stopped. More than 30 VIA Rail arrivals and departures at Union Station were also delayed — 11 by more than two hours, including on busy lines to or from Montreal, Ottawa and Windsor — according to data compiled by Greg Gormick , who runs the company On Track Consulting.

No CN freight trains experienced significant delays, while EXO commuter trains from the Montreal area and Amtrak passenger trains from the United States were able to run, Abecassis said.

After CN’s computerized dispatch system crashed, a handful of rail traffic controllers began issuing orders on paper, then radioing them to conductors to move trains to stations or to other stations. other safe areas of the track, where they were arrested, according to two railway sources who spoke on condition of anonymity.

EXO trains are dispatched directly by CN, which may have used manual techniques to run them, Abecassis said.

During the outage, CN worked with GO Transit to temporarily take over train dispatching, CN said. “This allowed GO and VIA services to partially resume starting late in the afternoon. »

“We will work with Metrolinx to put processes in place to prevent this from happening again,” concluded Mr. Abecassis.