AT&T cellular service restored after daylong outage; cause still unknown

A cellular outage Thursday hit thousands of AT&T users in the United States, disrupting calls and text messages as well as emergency services in major cities including San Francisco. The company said service was restored to all affected customers shortly after 3 p.m. ET.

“Keeping our customers connected remains our top priority, and we are taking steps to ensure our customers do not experience this again in the future,” the company said in a statement.

AT&T said late Thursday that based on an initial review, the outage was “caused by the application and execution of an incorrect process used as we were expanding our network, not a cyber attack.” The company will continue to assess the outage.

About 58,000 incidents were reported around noon ET, according to data from outage-tracking website Downdetector.com.

AT&T, which put up a website for system updates, did not say how many customers were affected by Thursday’s outage. The FCC said on X that it was investigating the incident and was in contact with AT&T and safety authorities.

Shares of AT&T closed 2.41% lower Thursday.

Phones affected by the outage displayed zero service bars in the top right corner of the device or the letters SOS. Customers were still able to make calls by enabling Wi-Fi calling.

A spike in outages began around 4:00 a.m. ET and peaked at around 74,000 reported incidents at 8:30 a.m. ET, according to Downdetector.

The AT&T outage affected people’s ability to reach emergency services by dialing 911, a post on social media platform X from the San Francisco Fire Department said.

“We are aware of an issue impacting AT&T wireless customers from making and receiving any phone calls (including to 911),” the fire department said.

Atlanta Mayor Andre Dickens said in a post on X that the city could receive and make outbound 911 calls but that AT&T customers in the area had reported issues.

“We have received calls from AT&T customers that their cellular phones are in SOS mode. Please direct all inquiries to restore service to AT&T,” Dickens said.

The Massachusetts State Police said that people were flooding their 911 center with calls trying to determine if the service worked from their cell phones.

“Please do not do this. If you can successfully place a non-emergency call to another number via your cell service then your 911 service will also work,” the state police said in a post on X.

Users of Verizon and T-Mobile reported a few thousand outages each as of 10:00 a.m. ET, according to Downdetector.

The reports were likely due to calls made trying to connect with other networks, both companies said.

“Downdetector is likely reflecting challenges our customers were having attempting to connect to users on other networks,” T-Mobile said in an emailed statement.

– Reuters, CNBC’s Steven Kopack and Chris Eudaily contributed to this report.