AT&T said it has restored 911 service to customers who were unable to place emergency calls from their phones.
The outage hit some parts of Texas, Indiana and other states in the Midwest, law enforcement authorities and government agencies reported Wednesday.
"Service has been restored for wireless customers affected by an issue connecting to 911," said a company spokesman.
Service outages are increasingly painful to wireless carriers, which are facing competition from rivals shouting about the quality of their own networks. Along with price, the quality of service is one of the key factors for a customer when choosing their carrier.
AT&T declined to comment on how many customers were affected by the issue, and didn't specify the cause of the outage.
The Federal Communications Commission will investigate the outage. "Every call to 911 must go through," Chairman Ajit Pai said in a statement Thursday.
Authorities warned AT&T customers that they may not be able to call the emergency number directly and offered alternatives for reaching emergency services. Agencies in Fort Worth, Corpus Christi and Plano, Texas, tweeted alternative phone numbers for people to call in the event of an emergency.
Agencies in Tennessee and Washington DC sent similar tweets.
Originally published March 8 at 7:47 p.m. PT.
Updated March 9 at 7:39 a.m. PT: Added a response from AT&T and noted the FCC's plans to investigate.
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