An employee from NB Power told CBC News they believe a squirrel climbed in a substation, causing a breaker to catch fire, and sending a trail of black smoke into the air.
"She's all gone to pieces," said New Maryland Fire Chief Harry Farrell. "The transformers are all burned out."
About 5,000 homes and businesses in the community just south of Fredericton lost their power. Some people in the city were also affected.
He said firefighters had to be careful as they dealt with the flames.
"We had to wait until they grounded the system," he said. "Then we were able to go up in the bucket and use extinguishers."
The power was restored to nearly all the customers by early Saturday afternoon. But Farrell said the remaining hundred could be in the dark for up to 72 hours as NB Power works on the grid.
"Get some ice, get coolers," he said, adding that people should not open their freezers during that time.