Australian telco Optus suffered another emergency call outage over the weekend, just over a week after a similar outage hit the carrier.

The company is already being investigated for the September 19 outage, during which four people died and more than 600 customers were impacted.

The latest outage hit the telco on Sunday (September 28), but was a much smaller scale. Optus stated that the incident centered around a mobile phone tower site in the Dapto area in New South Wales. 

"While all services have been restored, we are investigating the impact of the issue on calls made between 3am and 12.20pm today, including calls made to the Triple Zero network, and where necessary we are working with the police as part of the Triple Zero welfare check process."

Singtel-owned Optus said that the Triple Zero outage impacted 12 users. Triple Zero (000) is Australia's main emergency service phone number.

Continued scrutiny

Although Optus has opened an independent review into the outage on September 18, the carrier has come under severe scrutiny.

Australia's federal government told the carrier it can expect major financial penalties.

Australia's communications minister Anika Wells said Optus “failed the Australian people," while Prime Minister Anthony Albanese said Optus’s behavior was “completely unacceptable."

Optus stated that the outage was caused by a technical failure that occurred during a network upgrade.

The telco apologized for the outage in the immediate aftermath. In an update over the weekend, the carrier said that processes had not been correctly followed.

"Early investigations show that it appears that established processes were not followed," said Stephen Rue, Optus CEO.

"In order to establish why this occurred, we are speaking with the individuals involved. As to the full technical detail of the network failure, we will need to leave that for the investigation."

It's not the first time Optus has suffered a significant outage that has impacted Triple Zero services.

Last year, the carrier was slapped with an AU$12 million (US$7.93m) fine for an outage in 2023. The outage, which happened on November 8, 2023, lasted more than 14 hours.

The fallout from the outage was so severe for Optus that its CEO at the time, Kelly Bayer, resigned. Its head of networks, Lambo Kanagaratnam, also quit months later.