AT&T Inc.’s network has returned to normal operations following an outage earlier today that left a large number of users without reliable cellular reception.

The U.S. Federal Communications Commission launched an investigation into the service disruption shortly after it began. The U.S. Cybersecurity and Infrastructure Security Agency, in turn, is reportedly working with AT&T to understand what caused the outage. Officials have stated that there’s currently no reason to believe the network downtime was caused by a cyberattack.

Before AT&T rolled out the fix, thousands of customers were unable to make calls or send texts. The carrier advised users to work around the issue by enabling Wi-Fi calling, a feature that allows handsets to communicate via a local wireless router. Apple customers, meanwhile, reported that their iPhones switched to Emergency SOS mode, which makes it possible to contact emergency services even when there’s no cellular reception.

AT&T users started experiencing technical issues in the early morning hours. Downdetector, a service that tracks carrier outages and other types of technical issues, received an initial surge of downtime reports around 4 a.m. EST. The number of reports climbed to a peak of about 74,000 at 8:30 a.m. and began declining shortly afterwards. 

By noon, the number of user-reported downtime incidents tracked by Downdetector dropped to 58,000. Around the same time, AT&T posted an update on its website confirming that its infrastructure was beginning to recover. “Our network teams took immediate action and so far three-quarters of our network has been restored,” the company told users.

AT&T posted a second update at 3:10 p.m. EST to inform customers that the outage has been resolved. “We have restored wireless service to all our affected customers. We sincerely apologize to them,” the note reads. “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.”

Before AT&T began restoring its network, some customers of Verizon Communications Inc. and T-Mobile US Inc. also reported technical issues to Downdetector. In response, the carriers issued statements clarifying that their infrastructure wasn’t impacted by the outage. They believe most of the affected customers experienced technical issues while attempting to contact AT&T users.

Today’s outage comes about a year after a large-scale broadband disruption left thousands of T-Mobile customers without cellular and internet coverage. The incident was resolved within a few hours. At the time, T-Mobile attributed the downtime to an “interruption” in the fiber-optic network of a third-party organization.

Photo: AT&T