Copper thieves have once again forced the shutdown of O-Train service on the Trillium Line, OC Transpo has confirmed.

The line has been out of commission since 7:30 a.m. Tuesday. Ottawa police are investigating.

OC Transpo won't say exactly where the theft of valuable copper cable occurred because it doesn't want to encourage copycats.

"We've had occurrences where graffiti and those types of things occur, but nothing of this magnitude," said Troy Charter, OC Transpo's director of transit operations, by phone Wednesday. "There has been one other occurrence that has impacted service like we're seeing yesterday and into today."

OC Transpo's director of transit operation, Troy Charter, said Ottawa police are investigating the theft. (Simon Gardner/CBC)

That incident — also a copper theft — occurred in March 2017.

OC Transpo has been slowly replacing the above-ground poles that carried the copper signal cable, and Tuesday's theft occurred at the last such pole still standing.

"At the end of this year, we will have addressed that last final location where this exists," Charter said.

'Highly dangerous'

Charter didn't know how much cable was stolen, but said it was a "highly dangerous" crime that must have required some "pretty robust tools" to pull off.

"You're cutting through a fairly significant piece of copper wire to get this. It's not something you can just pull apart with your hands," he said.

"The system and the safety system functioned as intended. Immediately, once we lost that communication the trains came to a complete stop."

OC Transpo's website said service is expected to resume Wednesday but Charter didn't want to give an estimated time, saying that the cable has been replaced but "hours" of testing are required to get trains up and running again.

Trillium Line 2 continues to be temporarily replaced by 107 bus service due to vandalism. Details:<a href="https://t.co/9qivfXfYoQ">https://t.co/9qivfXfYoQ</a> —@OC_Transpo

O-Train service is being temporarily replaced by Route 107 buses running roughly parallel to the Trillium Line, which extends from Bayview to South Keys stations.

O-Train Trillium Line service is temporarily replaced by Route 107 due to a technical issue. <a href="https://t.co/9qivfXfYoQ">https://t.co/9qivfXfYoQ</a> —@OC_Transpo

Transit users can find other route options at the OC Transpo website.

Schedules are also available by calling 613-560-1000 or texting 560560 plus the bus stop number.