GRAY – Wireless telephone users across southern Maine were unable to call 911 for most of the day Tuesday because of a malfunction in a telephone system.

An early morning power surge burned out components at Pine Tree Telephone, which left cellular telephone users in Cumberland, York, Oxford and Androscoggin counties unable to get through to emergency response numbers. Between 5 a.m. and 2:30 p.m., callers received a busy signal when they dialed 911 or 77.

The malfunction also left wired telephones within the 657 exchange without a dial tone and unusable.

The problem may have occurred after wind toppled a tree over Route 26, temporarily interrupting electrical service. A power surge followed, public safety officials said.

The surge then burned out two of three identical components that are used to convert electricity to the direct current needed for telephone service. A single remaining component could not handle the entire system and ultimately broke down as well, said Pine Tree president Robert Souza.

Public safety officials said they were unaware whether the problems significantly interfered with the work of emergency responders or whether any members of the public suffered as a result.

State police in Gray receive between 200 and 300 calls on the 911 line each day from cellular telephone users in the four counties, usually disabled motorists or motorists reporting accidents they have seen.

Callers were able to reach state police using the barracks’ toll-free number, (800) 228-0857, which connects to the barracks through a Portland exchange. “We’ve had similar types of experiences, but generally speaking, this happens during an ice storm or a tremendously violent thunderstorm,” Souza said. “A lot of times it happens in the wee hours of the morning and a lot of customers are not aware it even happened.”