FARMINGTON — Thousands of homes and businesses in Franklin County went without power for nearly four hours Monday morning amid frigid temperatures, forcing businesses to close and schools to dismiss students early.

About 4,000 Central Maine Power Co. customers, primarily in Farmington, lost power at about 8 a.m., company spokeswoman Gail Rice said.

Utility crews restored power to all customers shortly before noon, with the outage also affecting a few small pockets in nearby towns, Rice said.

A mobile substation in use at the Sturtevant substation malfunctioned and caused the outage, making it the second time the equipment failed since being installed last month, she said.

The substation is on Farmington Falls Road, or U.S. Route 2, in Farmington, where the power company is relying on a mobile substation until it finishes installing a new transformer, Rice said.

Students at Mt. Blue High School were dismissed at noon Monday because of the power outage. A generator kept power running to hold classes in certain sections of the high school building in Farmington, but many classrooms had to be closed because they lacked energy and heat, Superintendent Michael Cormier.

Cormier made the call to dismiss the students after the power company initially reported that the outage would last until 2 p.m., he said.

Power was restored at the building before the nearly 740 students got dismissed, but the plan went ahead because it would have been difficult to recall the buses and re-heat the classrooms, Cormier said.

Also in Mt. Blue Regional School District 9, students in pre-kindergarten to third grade at W.G. Mallett School were bused to another school in Farmington for lunch during the power outage, Cormier said.

The mobile substation first failed Nov. 15 about 5 p.m. Thousands of customers in eight towns lost power for nearly two hours that evening.

The power company is looking into what caused the outage Monday morning and whether it is related to the initial failure, Rice said Monday afternoon. She was unaware of what caused the initial failure and did not return a request for details.

Work to install a new transformer, meanwhile, will continue at the substation until the entire upgrade project is complete, Rice said. There is no timetable for the next step, she said.

Close to a dozen mobile substations are being used in Maine by the power company, which seldom has problems with the equipment deployed during emergencies or maintenance work, Rice said.

Businesses in downtown Farmington posted notes on doors telling customers about closings from the outage. Motorists turned an intersection at Main Street and Broadway with unlit traffic lights into a four-way stop.

Temperatures Monday morning across Maine were at the lowest levels so far this year, dipping below zero overnight, according to John Cannon, a meteorologist with the National Weather Service office in Gray.

By 9 a.m., temperatures in the Farmington area hovered in the mid-teens, reaching the low 20s by about 11 a.m., he said.

Brenda Czado, a director of a home health aide group, said Monday that power outages can be a serious problem for senior citizens, especially during the winter months.

“The freezing temperatures are the worst thing this time of year and making sure everybody is OK is important,” she said.

As an administrator for Androscoggin Home Care and Hospice, Czado oversees the 225 home health aide patients in the Franklin County area, with about 75 falling within Farmington.

Her office calls patients during power outages and other emergencies. Neighbors and family members are also listed as contingency contacts to check on patients who can’t be reached, she said.

Emergency health care networks also exist to get people to heating shelters when there is extended power outages during the winter, Czado said.

“It’s all hands on deck for health care providers during an emergency,” she said.

Czado said for information people can call Androscoggin Home Care and Hospice at 777-7740.

David Robinson — 861-9287

[email protected]