"Some of our customers are experiencing wireless service interruptions this morning. Our network teams took immediate action and so far three-quarters of our network has been restored. We are working as quickly as possible to restore service to remaining customers," AT&T said in a statement to NBC News. 

Although AT&T took steps to resolve network issues, the company did not disclose the cause of the outage.

According to the US Cybersecurity and Infrastructure Security Agency, there were no indications of a cyberattack. 

"CISA is aware of the reports and we are working closely with AT&T to understand the cause of the outage and its impacts, and stand ready to offer any assistance needed," Eric Goldstein, the agency's executive assistant director for cybersecurity, said in an emailed statement.

One theory suggests that space weather could be responsible for the nationwide cell outage.

Around the time of the outage, two X-solar solar flares were reported by NASA. 

Solar flares can disrupt ground-based and or satellite-based communication networks. 

Meanwhile, ignore the X-solar solar flares. The FBI & DHS are on it! 

FBI, DHS PROBES IF AT&T ISSUE AN ATTACK OR TECH MALFUNCTION:ABC

AT&T DISRUPTION PROMPTS AGENCIES TO PROBE IF CYBER ATTACK: ABC