DRACUT -- Workers Tuesday began repairing four senior-housing units on Mammoth Road that were damaged in a Feb. 23 fire that was ruled caused by wiring between two walls.

The fire was not related to a treatment being done in one of the units for bed bugs, according to the Fire Department and the Housing Authority.

The treatment, which took place in two housing units, involved heating the rooms up to about 130 degrees for a few hours to get rid of the pests, Fire Chief David Brouillette said.

But that wasn't the cause of the fire, which took place at the same time. A Fire Department investigation found that wiring inside two walls between adjoining housing units somehow started the fire. Heat detectors in the units are designed to go off at 135 degrees, and they did not go off during the bed-bug-treatment process, Brouillette said.

The company conducting the treatments was using its own generators for power, which were outside the units, he said. One of the company's workers spotted light smoke in one of the units and called the Fire Department, Brouillette said.

It isn't yet clear when tenants in the four affected units will be able to move back in, said Housing Authority Executive Director Mary Karabatsos. The units will receive new rugs and paint after the repairs are made, she said.

"We're doing everything we possibly can to help people feel settled where they are," Karabatsos said, adding that insurance paid by the Housing Authority covers temporary-housing costs for tenants.

"Residents understand it was an accident, sort of a freak accident, and residents have been understanding."

Bed bugs were found only in those two units, with testing done in other units in the complex, she said.

The fire took place around 1 p.m., and firefighters had the fire out within just over a half-hour, according to the Fire Department.

Follow Grant Welker at Twitter.com/SunGrantWelker.