The company’s website indicated that the problem affecting landlines began just after 1 a.m. on Thursday.
Affected areas included Durham Region, Peel Region, Halton Region, Hamilton, Niagara, Guelph, Gananoque and Chatham.
“Wireline 911 services are experiencing a failure which may result in being unable to call 911 from your landline,” the website said.
A statement from Telus said maintenance activity on its network was to blame for the disruption to wireline services, including calls to 911.
Service was fully restored by 5:42 a.m., the statement said.
“We know how critical connectivity is for our customers, and would like to thank our customers for their patience and understanding,” Telus said.
The Hamilton Police Service and Peel Regional Police both posted messages on social media advising residents of the outage.