Australian telecommunications giant Optus said Monday it had suffered a network outage that prevented calls to emergency services, just over a week after a similar interruption of service linked to four deaths. The firm said it had "confirmed with police that all callers who attempted to contact emergency services are OK."Advertisement AdvertisementAdvertisement Advertisement"Optus continues to investigate the cause," it added. This month Optus said it suffered an outage that impacted 600 people across South Australia, Western Australia and the Northern Territory for at least 10 hours. The outage prevented calls to emergency services, with four deaths now linked to the outage. Advertisement AdvertisementAdvertisement AdvertisementLast week, Optus announced details of an independent review that will probe the series of events that took place and determine why emergency calls did not connect.