Fire department officials confirm approximately 40,000 CenturyLink customers in Mesa were unable to access the 911 system on Wednesday.
The situation started around 9 p.m. Wednesday night.
As of Thursday morning, all landline customers regained 911 access.
Mesa Fire Department spokesman Forrest Smith said users trying to call 911 received a busy signal.
Smith said the outage affected landline users only. Cell phone users were able to access 911 in case of an emergency.
Juarez said the problem could have been at their central office location.