Normal service at Kennedy subway station in Scarborough likely won't be restored until Tuesday morning following a derailment, says TTC chair Adam Giambrone.

The derailment occurred about 1:30 a.m. as the last train was heading westbound out of Kennedy. It was in the tunnel but not far from the station, he told CTV.ca Toronto on Monday.

It occurred "likely because there was either a piece of the train dragging or there was something the train had picked up and was dragging along the track," he said.

When the train derailed, there was some damage to the subway tracks and to the cables used in the signalling system, he said.

There were four passengers on board, but the train hadn't gotten up to speed and no one was injured, he said.

"Right now we've been repairing the track," he said, adding the next step will be lifting the train back on the track.

More than 70 people are working on repairing the damage.

"Hopefully we'll have service restored by tomorrow morning."

In the meantime, there will be no subway service in either direction between Kennedy and Warden stations.

TTC transit reporter Mika Midolo told CTV.ca Toronto on Monday that the TTC will use a fleet of 32 shuttle buses to move passengers between the two subway stations.

"Passengers will have to stick to the bus-bay platforms at Kennedy Station and supervisors will directly them to the shuttle buses," she said.

"There's about a 15-minute wait for a bus, because as you know, buses can't carry as much as subway trains."

Some commuters said they were frustrated as the delays made them late for work Monday morning.

"It's difficult to get to work on time, especially when you're running late," said one woman.

"I thought to myself, 'why on the morning when I have to take the kids on the subway does this happen to me?'" one woman said while holding a small child in her arms.

Other passengers said the derailment made them worry about the overall safety of subway trains.

Giambrone said derailments do occasionally occur.

He couldn't estimate how many subway derailments occurred in 2007 other than to say the number is relatively low and that the subways are safe. He said the 126-subway car fleet has been inspected.

"One area the TTC has never compromised on is keeping the tracks in working order," Giambrone said.

With a report from CTV Toronto's Roger Petersen and Naomi Parness