A temporary network disruption that affected AT&T customers in the U.S. Thursday was caused by a software update gone wrong, according to preliminary information from two sources familiar with the situation.
Sources have told ABC News that there was nothing nefarious or malicious about the incident.
AT&T declined to comment on the situation to ABC News Thursday evening.
The disruption prompted federal agencies to investigate whether the outage was caused by a cyberattack.
In an earlier statement to ABC News, AT&T confirmed the outage and advised customers to make calls over Wi-Fi.
“Some of our customers are experiencing wireless service interruptions this morning. We are working urgently to restore service to them. We encourage the use of Wi-Fi calling until service is restored,” an AT&T spokesperson said.
Later Thursday afternoon, AT&T issued an update saying that its network had been…