Reports on Downdetector.com, a platform monitoring outages, indicated instances of no service or signal after 04:00 EST (09:00 GMT).

AT&T issued an apology to its customers and confirmed that services were fully operational again by early afternoon. The company stated its commitment to taking preventive measures to avoid similar incidents in the future. The cause of the outage is currently being investigated.

Verizon and T-Mobile informed the BBC that their networks were functioning normally. However, they acknowledged that some customers may have experienced service issues while attempting to communicate with users on different networks.

According to Downdetector, AT&T received over 74,000 customer complaints, with significant clusters in southern and eastern regions of the country.

Smaller carriers like Cricket Wireless, UScellular, and Consumer Cellular also reported interruptions in service. Complaints ranged from difficulties with calls, texts, to internet access, with many users reporting no service or signal.

Downdetector's data showed that major cities including Los Angeles, Chicago, Houston, and Atlanta experienced high numbers of outages.

Some individuals also faced challenges with 911 services, prompting officials to advise the use of landlines, social media, or cell phones from alternative carriers in emergencies.

The widespread outage has garnered the attention of the US government, with the FBI and Department of Homeland Security launching investigations, as confirmed by John Kirby, spokesperson for the US National Security Council.

Eric Goldstein, executive assistant director for cybersecurity at the US Cybersecurity and Infrastructure Security Agency, stated that they are collaborating with AT&T to understand the root cause of the outage and are ready to provide assistance as necessary.

Although a confidential memo reported by ABC News suggested no signs of malicious activity, CISA officials are actively investigating the incident.