HOULTON — About 4,400 electricity customers in southern Aroostook and northern Penobscot counties were left in the cold and dark on Christmas Eve when a transformer failed in Houlton, according to local officials.

Customers of Maine Public Service Co. and Eastern Maine Electric Cooperative were left without power from about 5 p.m. to about 1 a.m. on Christmas Day.

Because of the extreme cold temperatures, the Aroostook Emergency Management Agency set up shelters for people without alternative sources of residential heat.

“This is the worst time for this to happen,” said Vern Ouellette, director of the emergency program.

Emergency shelters were set up in the Houlton National Guard Armory, fire stations in Linneus, Littleton, Monticello, Hodgdon, Haynesville and Island Falls and at the Patten Rest Home.

Ouellette said he was not aware of anyone taking advantage of the shelters.

Because of the Christmas holiday, he said it was difficult to contact people to open the shelters. He said he received help from the Maine State Police and the Aroostook County Sheriff’s Department.

MPS technicians and line crews worked in sub-zero weather Christmas Eve to restore power to approximately 2,800 customer accounts from Houlton to Grindstone affected after the 69KV/44KV transmission transformer failed at the Mullen Substation in Houlton.

Another 1,600 Eastern Maine Electric Cooperative customer accounts, fed from the MPS system, also were without power. The electrical outage affected customers in Oakfield, Island Falls, Dyer Brook, Patten, Benedicta, Crystal, Merrill, Smyrna, Sherman, Smyrna Mills, Amity, Hodgdon, Linneus, Medway, Grindstone, Stacyville and a portion of the EMEC system, MPS officials said.

MPS crews were able to reconfigure and switch to a backup transformer located at the substation to provide service to customers from Houlton to Island Falls by 12:15 a.m. Christmas Day, according to MPS officials.

All other customer accounts from Island Falls south were restored by 12:45 a.m. The cause of the transformer failure is under investigation, according to MPS officials.