A ship dragging its anchor on the seabed in the English Channel has cut the three main internet cables to the Channel Islands overnight.
Broadband speeds are expected to be slower as a result and cable owners JT, Sure and BT say it could take up to three weeks to repair.
Telecom company JT says engineers have been dispatched to repair the cables.
Jersey's coastguard says there will be an investigation to see if the ship dropped anchor in a banned area.
Master Pilot Peter Moore said the boat, believed to be the King Arthur, anchored north of Alderney yesterday evening..
He says there are several undersea cables marked on the charts in that area with clear instructions not to fish or drop anchor.
All communications traffic from JT, the main operator in Jersey, is going through a single link to France with slower connections and call problems reported across the Channel Islands.
Daragh McDermott from JT said: "With all traffic now using this connection, customers may notice some impact on services.
"It is exceptionally unlucky and unprecedented for three submarine cables to the UK to be cut in the same day."
A number of people have reported losing internet completely earlier this morning with one woman saying she had to set up a mobile hotspot to get a connection.
Master Moore says it is still unclear where the King Arthur dropped anchor but there would be an investigation.
The BBC has approached the owners of the King Arthur, Mediterranea di Navigazione, for comment.
Guernsey's largest telecom company Sure says it has been working with JT to reroute its data through the Sure network as it was only their voice cables that were affected by the incident.
This is not the first time a ship has cut a Channel Islands telecom cable this year. In January one was cut when a ship dropped anchor in stormy weather.
Three cables went one after the other on Monday with the first going at 16:00 GMT and the last by 21:00 GMT as the anchor was dragged across the seabed.
Mr McDermott said repairing the cable would be a "tricky, tricky job" involving engineers going out in heavy winds to remove the cables from the sea and splice them back together.
Jersey Treasury Minister Senator Alan Maclean, who acts as government shareholder for JT, said in the States: "If there is damage attributable to a particular owner then I'm sure they will pursue it."