Shefa spokesman Pall Vesterbu told BBC Radio Orkney a repair vessel would be at the site of the break around 5.5 miles (99km) from Orkney this week to assess the damage and and fix the cable.
Mr Vesterbu said it was probably a fishing boat which caused the damage but the company could not be sure until inspections have been carried out.
He is calling on fishing boats to avoid fishing directly over the cables and to keep their Automatic Identification System (AIS) indicators on at all times so they can be warned if they are fishing too close to the cable network.
Internet provider OpenReach initially said 10,000 customers had been affected but then scaled that back to “hundreds”.
The Balfour Hospital’s switchboard and phone system has been restored after it went down on Saturday, with patients asked to call a mobile number while it was being fixed.
The Shefa-2 cable provides a wholesale link which is used by telecoms companies to deliver services to their customers.
This is used by OpenReach to deliver the broadband network to the islands, which is then sold on by individual companies like EE, Vodaphone, Sky and PlusNet in different packages.
That is one reason why customers and businesses have had different experiences this weekend – with some experiencing no interruption, others coming back on overnight, and some taking longer to be restored.