DERBYSHIRE fire service tonight said the cause of a fire which cut tens of thousands of Derby phone lines is still not known.
An investigation is ongoing into the cause of the blaze at the BT exchange in Colyear Street, Derby.
The fire, which broke out at 3.30am today, was on the first floor of the exchange.
Businesses across the county were affected by the problems, including Rolls-Royce in Derby.
The fire service spokeswoman said the blaze was not caused deliberately.
