National Grid has admitted it is to blame for leaving thousands of Virgin Media customers without internet, TV or phone access for three days.
A fibre optic cable was severed by workmen in Goodmayes Road, Seven Kings, on Wednesday.
Virgin Media engineers arrived on site within the hour and had been working since to fix the cable.
Service was restored to customers on Saturday afternoon.
A National Grid spokesman said: "We were carrying out some vital gas mains repair work in Goodmayes Road, Seven Kings on Wednesday.
"Despite taking reasonable steps to detect cables, a fibre optic cable was cut during the work.
"The cable was located near to the gas main we were working on.
"We informed Virgin Media of the incident as soon as we became aware and apologise for any inconvenience this incident caused."
The spokesman confirmed an investigation into the incident is being conducted.