Residents in Leyland are unable to call 999 tonight, police have said.
A spokesman for South Ribble Police said: "BT have notified us of a fault on their lines which is stopping people in the Leyland area from being able to contact the 999 service from their landlines. This is also affecting 999 calls to the fire and ambulance services from landlines.
"BT are currently working to restore full service and estimate this will be done by around 12.30am (Friday morning).
"In an emergency please dial 999 from a mobile phone or, if you do not have a mobile phone, we would advise you ask a neighbour or seek help in person from a police station. We would also urge residents to look out for elderly or vulnerable neighbours or relatives who may not own a mobile phone and may need assistance in case of an emergency.
"We will update you as soon as we can."