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Emergency services were left "very vulnerable" at the weekend as flooding caused network outages across the South, making tens of thousands of people lose internet and mobile coverage.
For more than 12 hours from Saturday night to yesterday morning, all Spark and some 2Degrees customers south of Ashburton lost coverage.
While the 111 emergency line is meant to switch to other networks during such events, there have been reports even this failed in some instances.
A Spark spokeswoman said at 10.15am almost all the affected services were restored by a workaround using spare fibre strands and additional cables.
Last night she said the sites of the damage, at Ashburton and Timaru and between Darfield and Geraldine where they crossed the Rangitata River, were still inaccessible and some customers still lacked coverage.
A 2Degrees spokeswoman said it also had weather-related issues that affected "a large portion" of its southern customers overnight.
She was unable to provide more information last night.
Otago Regional Rescue Helicopter chief pilot Graeme Gale said the cut services left it "very vulnerable" but it did not miss any missions.
"But we lost communication initially with ambulance control, with the hospital, with our pilots and with our paramedics. It was really significant."
Luckily, many paramedics were on the Vodafone network, he said.
The Warehouse in Mosgiel opened late to supply the team with Vodafone phones and he "couldn’t thank them enough".
Fire and Emergency New Zealand shift manager Dan Reilly said yesterday the outage was "obviously having an effect" on its operations.
"We have a lot of devices connected to the Spark network, but are making do with our alternative means of communication."
The biggest concern was members of the public needing to call through the 111 system, he said.
"It’s supposed to switch over, but I can’t speak to how well that’s working."
The Southern District Health Board said on social media the outage affected its communications, but its
services were running as normal by midmorning.
A police spokeswoman said there were no significant issues in the South as a result of the outage.