AT&T said Thursday that its wireless network was back up after an outage knocked out cell service for its users across the U.S. for hours.
“We have restored cell service to all of our affected customers,” the Dallas-based company said in a statement posted on its website Thursday afternoon. “We sincerely apologize to them.”
Outage tracker Downdetector found that the outages, which began around 3:30 a.m. ET, peaked with around 73,000 incidents reported. AT&T had more than 58,000 outages in locations including Houston, Atlanta and Chicago as of noon ET. With more than 240 million subscribers, the provider is the largest in the country.
As of 3:30 p.m. ET, reports had dropped to fewer than 3,000.
AT&T-owned Cricket Wireless experienced more than 9,000 outages at one point, but reports also tapered off later in the afternoon. Users from other wireless carriers, including Verizon and T-Mobile, also reported problems, but those companies said their networks were operating normally and the problems were likely due to customers trying to connect to AT&T users.
Some iPhone users began seeing SOS messages appear on their phone's status bar. The message indicates that the device is having trouble connecting to the carrier's network, but can make emergency calls over other cellular networks, according to Apple Support.
So far, no reason has been given for the failures. But Lee McKnight, an associate professor at Syracuse University's iSchool, cited cloud misconfiguration or human error as the most likely cause of the outage.
“A possible but far less likely outcome is an intentional malicious hack of the ATT network, but the diffuse pattern of outages across the country suggests something more fundamental,” McKnight said in an emailed statement.
The Federal Communications Commission contacted AT&T about the outage, and the Department of Homeland Security and the FBI were also investigating the case, said John Kirby, spokesman for the National Security Council.
The FBI admitted to having been in contact with AT&T. “Should we become aware of any malicious activity, we will respond accordingly,” the agency said.
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Associated Press writers Zeke Miller and Lindsay Whitehurst in Washington, D.C., contributed to this report.