Amazon is apologizing for the disruptions to its S3 storage service that knocked down and -- in some cases affected -- dozens of websites earlier this week . The company also outlined what caused the issue -- the event was triggered by human error. The company said an authorized S3 team member using an established playbook executed a command which was intended to remove a small number of servers for one of the S3 subsystems that is used by the S3 billing process. "Unfortunately, one of the inputs to the command was entered incorrectly and a larger set of servers was removed than intended," the company said in a press statement Thursday. It adds: