Thousands of homes and businesses in Birmingham were still without phone lines this morning after a BT exchange was sabotaged.
Police are considering the possibility that a former BT employee with a grudge was responsible for about 35,000 homes and businesses having their land-lines cut off in the early hours of yesterday.
The saboteur risked electrocution to hack through the cables at the Handsworth exchange.
It left the affected properties unable to contact 999 and having to rely on mobile phones in an emergency. Engineers were working throughout yesterday to restore the service but said up to up to 10,000 addresses could still expect to be without lines today.
A spokeswoman for West Midlands Police said raiders had cut through a bundle of about 30 cables.
The areas affected by the damage included Aston, central Birmingham, Perry Barr, Handsworth, Ladywood, Blackheath, Stone Croft, West Bromwich, Tipton and Wednesbury.
Customers, including the City Hospital, were left either completely without phone services or with only partial use of their phones. The break-in to the exchange, which is secure and usually unmanned, happened at sometime between 1.10am to 2am yesterday.
Inspector Paul Robb, of West Midlands Police, said: "It appears that the person who caused the damage has gained access to the rear yard of the exchange and gone through a hatch on the ground into the building.
"They got into a box with 25 or so fibre optic cables and severed them. It was deliberate, and they seemed to know what they were doing." A spokesman for BT said: "This attack was obviously done by somebody deliberately."
Initially engineers believed that just 14,000 lines had been affected. It was only when repairs to BT information lines had been made that it became evident that more than double that number had been knocked out.
Engineers were working throughout the night to restore communication, repairing each fibre optic cable one by one.
A spokesman for BT said engineers had been prioritising cables containing large numbers of phone lines identified as belonging to people who were old or infirm, or in regular need of hospital treatment. By 6pm last night 3,600 residential and business addresses had been reconnected.
People unable to get through on 999 from their land-lines were urged to use a mobile phone.