An explosion in an electrical room at the Shaw building in downtown Calgary affected some of the city's telecommunications, including 911 services.
The city activated its Municipal Emergency Plan when the fire broke out Wednesday afternoon.
Calgary's Emergency Medical Services was affected, along with other businesses, banking services and agencies using Shaw as their internet provider.
At the time of the explosion, the City of Calgary warned that 30,000 Shaw landline customers in the downtown area may not be able to call 911.
Most roads and businesses were open on Thursday, but officials say getting the health computers back online is the most critical issue. The outage has had no impact on patient care and no surgery delays have been reported.
There is no word on the cause of the explosion yet.
With files from The Canadian Press