GO Transit says it was a lightning strike that caused major delays west of Union Station on the Lakeshore East and West lines on Monday afternoon.
For over two hours during rush hour, no trains were running westbound from Union Station.
Trains began running again at 8:13 from Union Station, but residual delays were still expected.
Sunyya Kukaswadia, a Metrolinx spokesperson, says the cancellation out of Union Station also caused residual delays on the Lakeshore East line.
Shuttle buses were not running during the delays due to the sheer number of the impacted passengers. GO Transit officials say it was close to 10,000 people.
Riders have taken to Twitter to express their frustration over the long delays and reportedly extremely hot trains.
Kukaswadia added she understood riders were frustrated during the lengthy delay.
“We know it was incredibly frustrating. The weather was not great. We apologize truly for the inconvenience,” she said. “We tried our best to get everyone moving as quickly as possible after the lighting strike impacted our service, but we really do appreciate our customers patience and we have been listening.”
Officials are encouraging riders affected by the delays to file a claim on their Service Guarantee page starting Tuesday morning so they system has time to process the information.