Metro service is back up and running Tuesday after an electrical problem shut down parts of the network during the Monday evening rush hour.

The STM shut down a stretch of the orange line in the afternoon after smoke was seen in a tunnel between the Sauve and Henri Bourassa stations.

Reporting live from the corner of Berri and De Maisonneuve, CTV Montreal reporter Annie DeMelt said the STM originally believed a small fire had caused the smoke, but later concluded they were dealing with a different problem.

"There was actually sparks on one of the wires and so they had to have it checked out by firefighters," DeMelt said.

Service on stretches of both the yellow and blue lines was disrupted by the incident, but it was restored shortly after 5 p.m.

The orange line was back up by 9:00.

The STM arranged for shuttle buses to transport passengers affected by the temporary shutdown of the orange line.

DeMelt said a sea of frustrated transit users had lined up in the cold near the Berri-UQAM station, waiting to board the packed buses.

"They're lining up around the block," she said, adding that some had already been waiting for half an hour.

One woman told DeMelt she anticipated having to wait for a few hours before finally getting home.

"I hope there's not too much traffic on the way. I'm expecting to be home around 9:00," she said.