After conflicting reports, it now seems almost certain that the undersea eruption over the weekend did cause a break in the cable that connects Tonga to the outside world - and that it will take at least four weeks to repair.
And that timeline could be stretched further because of the proximity of the break to the undersea volcano, and the danger of further eruptions.
In the meantime, the dust cloud from the volcano means that even satellite phone and internet connections are intermittent.
The best-case scenario - and one that seemed possible at first - was that the fibre was intact, and the internet outage was caused by power outages that disabled the cable.
On Sunday, testing indicated there could in fact be a break, but it was not clear if it was on land, which would take days to repair, or out at sea - the worst-case scenario - which could mean weeks before it could be reconnected.
This morning, Southern Cross Cable executive Craige Sloots told the Herald that "Fintel and TCL [Tonga Cable Ltd] undertook testing yesterday afternoon which seems to confirm a likely cable break around 37km offshore from Tonga".
TCL is arranging the repair, but industry veteran Sloots said the process could take a minimum one to two weeks (update: Tonga Cable now says at least four weeks). The repair would likely be carried out by a cable laying vessel called the CS Reliance, which is currently off the Papua New Guinea capital of Port Moresby - some 4000km away.
The CS Reliance is operated by US company TE SubCom, which holds a maintenance contract covering 19 cable systems across the South Pacific.
Tonga Cable director Samiuela Fonua - who is currently in Auckland on a family matter - told the Herald he received confirmation last night that TE Subcom would assist with the repair of the broken international cable, plus damaged domestic cables.
But timing was up in the air.
"The last cable cut [an alleged act of sabotage in 2019] took nearly two weeks to repair," Fonua said.
"This time, I am not sure yet because we have to take into account site conditions, the fact that the repair ship will be entering the Tongatapu waters not too far away from the eruption site - and if the volcano is still active."
In the meantime, Tonga has very limited phone and internet access. Fonua said the dust cloud from the volcano was interrupting backup satellite communications.
Kiwi telcos Spark, Vodafone NZ and 2degrees are all offering free mobile and landline calls to Tonga this week.
However, phone service is still heavily disrupted.
"Unfortunately communication in Tonga is difficult right now due to the damage caused by weather events, so immediate contact may not be possible," a Spark spokeswoman said.
Vodafone is expected to announce relief through the Vodafone Foundation this afternoon.
The 837km Tonga Cable is 80 per cent owned by the Tongan government, and pan-Pacific telco Digicel a minority stakeholder.
The Tonga Cable intersects with a cable to Fiji run by Fijian telco Fintel, plus the trans-Pacific Southern Cross Cable, in which Spark is a major shareholder.
Sloots said the Southern Cross Cable was unharmed, and that his company has no financial or other relationship with TCL, but his company was monitoring the situation the best it can amid "scarce communication" with Tonga.
Until recently, New Zealand also had only one major internet connection to the outside world - the twin legs of the Southern Cross Cable.
That has changed over the past five years with the launch of the Tasman Global Access cable between Auckland and Sydney (a joint-venture between Vodafone, Spark and Telstra), and the launch of the Hawaiki Cable connecting Australia, NZ and the US. Hawaiki was backed by rich-list investors including Sir Eion Edgar and Malcolm Dick. Last year it was sold to Singapore's BW Group.