TTC subway suspension: What caused your frustrating commute this morning

The TTC says acable chamber fire at Richmond and Victoria streetsearly this morning caused your nightmare TTC commute into the downtown core.

The fire is out, and subway and streetcar service has resumed after crews spent the morning repairing cables hit by the fire in the morning.

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Toronto firefighters discovered the fire when they responded to a carbon monoxide call at 50 Richmond St. E.just after 1 a.m. Crews then determined that it was an underground hydro vault on fire and hydro crews were called to the scene.

TTC spokesman Brad Ross told CBC News that the underground hydro station is a "major source" of power for the TTC.

He says the Richmond substation feeds power to Line 1 between Dundas and Osgoodestations. It also feeds most of the downtown streetcar lines: Dundas, Queen, King, Spadina, Harbourfront,Wellington, Richmond, Adelaide, Bay,York, McCaul, Church, andParliament.

That's why, when there's a fire in the chamber, all power has to be shut off to allow electrical crews to investigate and make repairs, said Ross.

Toronto Hydro said it has cables in the chamber but none of its equipment has beendamaged. SpokeswomanToriGasssaidits workers were on scene to assist the TTC.

What is a cable chamber?

According to Toronto Hydro, a cable chamber, which isthe size of a small room, is an underground opening to the cablesystem.

Electrical cables that run under the sidewalks below ground are fed through large pipes called ducts.

At specific points throughout the city, the cables run into and out of a cable chamber providing an access point for repairs, inspections and new installations.

Toronto Hydro says there are about 10,000 cable chambers in the city.