About 37,000 Sky consumers across London are not able to access phone and broadband services, after thieves cut through and stole BT's Openreach fibre optic cables on Tuesday.
In addition to Sky, the outage also affected several TalkTalk consumers who were left with no access to phones, even though several calls were being redirected.
Blaming a 'malicious attack' for the outage, BT suggested that the thieves were looking for expensive copper materials from the exchange in Bedford.
With several engineers already working onsite to fix the issue, BT suggests that the work could continue until at least Friday evening, The Guardian reported.
A Sky spokesperson said that following a malicious attack on Openreach's network, there's currently a broadband and phone outage in parts of London.
"Sky and other companies are affected," Sky added.
"Openreach engineers are working to repair the network as a matter of urgency.
"We apologise to all affected customers."
Several exchanges in Stamford Hill, Dartford, Ewell, Mitcham, Wimbledon, Hampstead, Battersea, Chiswick and Beulah Hill have been hit with outage.