A temporary network disruption that affected AT&T customers in the U.S. Thursday was caused by a software update, the company said.

AT&T told ABC News in a statement ABC News that the outage was not a cyberattack but caused by “the application and execution of an incorrect process used as we were expanding our network.”

“We are continuing our assessment of today’s outage to ensure we keep delivering the service that our customers deserve,” the statement continued.

The software update went 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.

The outage was not caused by an external actor, according to a source familiar with the situation. AT&T performs updates regularly, according to the source.