The explosion caused an electrical fire on Wednesday at the building on Sixth Street and Third Avenue S.W. on the 13th floor in an electric room.
No one was hurt.
It left up to 30,000 landline telephone customers unable to call 911 and knocked out the city’s 311 information services line.
Shaw has almost finished restoring landline telephone services in the downtown core, and 911 service is now fully operational, the city said.
The emergency call centre was flooded with calls from people calling to check their phone service.
“It is imperative calls to 9-1-1 be limited to emergencies only,” the city reminded Calgarians.
The 311 service has been fully restored.
“The Calgary Emergency Management Agency has fulfilled its role in co-ordinating a multi-agency response to this situation,” the city said in release.
The incident also knocked out computers at Alberta Health Services (AHS), forcing ambulance drivers to take patients to the nearest hospital.
AHS officials said the computer problems are still creating delays in the medical system in Calgary and southern Alberta.
Many elective surgeries will likely have to be rescheduled, but urgent surgeries will not be affected. Medical tests are being prioritized, officials said.
Backup system failed to take over
Alberta Health Minister Fred Horne said officials will be reviewing their computer system, but for now they are concentrating on this current emergency.
Fire Chief Bruce Burrell, who heads the Calgary Emergency Management Agency, said the Shaw building is a "key hub" for national, provincial and municipal networking infrastructure.
“Certainly it's a relatively new building. It was specially designed special purpose built for this, engineered specifically to have double redundancies in it. So whatever has failed I'm sure will be quite a topic for discussion,” he said.
Peter Bissonnette, president of Shaw Communications, apologized for the breakdown.
It’s not yet clear why the backup system failed to take over, but he said the activation of the sprinkler system might have played a role. He said they have to be careful about bringing services back.
“We absolutely apologize for what has happened, and we're doing our best to restore services and we are in an emergency restoration process. So it may seem it's taking a little bit longer, but that length is actually necessary to ensure that things are done safely.”
Bissonnette said it's still unclear what caused the initial fire.