British Telecom says it could take several days before phone services are fully restored following the fire in a BT tunnel in Manchester.
Call centres have been badly affected by the fire
Engineers worked through Monday night to try to restore some of the 130,000 telephone lines which were blocked after Monday's fire.
"At this stage it is not going to be a few hours it is going to be a matter of a few days," said BT spokesman Paul Reynolds.
He said some lines had been restored by re-routing calls.
BT said it expects some phone lines to be restored on Tuesday, but added it could not put a figure on how many premises are still without a phone line.
Engineers entered the pitch black tunnels filled with smoke late on Monday afternoon to assess the damage, and worked through the night assessing the damage.
The are working in teams of 36 to restore hundreds of damaged fibre optic cables.
The fire has caused massive disruption - with telephone lines, internet services and Manchester's ambulance service affected.
The disruption is not confined to Manchester, as large parts of the North West have been affected.
In Macclesfield, Cheshire, the fire affected social services emergency alert lines used by pensioners in their own homes.
Two hundred mobile phones are to be issued to priority cases in Manchester and Cheshire.
Several call centres were closed by the fire as they were unable to receive or make calls.