Reuters ATT said late on Thursday an outage that disrupted calls and text messages for thousands of U.S. users and prompted federal investigations was not caused by a cyberattack.

The carrier had restored wireless service for all affected customers, several hours after an outage that affected more than 70,000 users at its peak.

Based on our initial review, we believe that today39;s outage was caused by the application and execution of an incorrect process used as we were expanding our network, the wireless carrier said in a statement on its website.

ATT, whose 5G network covers around 290 million people across the United States, has been grappling with interruptions to its service for more than 10 hours.

We are taking steps to ensure our customers do not experience this again in the future, ATT earlier said on its website.

The Federal Communications Commission said it was investigating the incident, while the U.S. Cybersecurity and Infrastructure Security Agency CISA said it was working with ATT to understand the cause.

White House spokesman John Kirby said the FBI and the Department of Homeland Security DHS were looking into the ATT outage. CISA is a unit of DHS.

We are being told ATT has no reason to think this was a cyber or security incident, said Kirby, adding that the FCC was in touch with the company.

But the bottom line is we don39;t have all the answers, he said about the cause of the outage.

ATT declined to comment on the FCC39;s investigation…