Technicians working on a firewall upgrade made at least ten mistakes, contributing to two deaths, according to a report on a September incident that saw Australian telco Optus unable to route calls to emergency services.

As The Register reported at the time, Australia’s equivalent of the USA’s 911 and the UK’s 999 and 112 emergency contact number is 000 – Triple Zero – and local law requires all telcos to route emergency calls to that number. For 14 hours on September 18, Optus could not route some customers’ calls to 000 and was unaware of any problems on its network. The company eventually learned of the situation from customers who complained to its call center.

During the 000 outage, 455 calls to emergency services did not go through, and two of those callers died.