More than 3,500 customers in northern Penobscot County suddenly lost power Thursday morning when a squirrel got into some electrical equipment at a Millinocket substation, an official said. The widespread outage, which occurred around 9:45 a.m, affected Emera Maine customers in the Millinocket region, spokeswoman Kendra Overlock said. Crews hope to restore power to all 3,586 customers by 1:30 p.m., she said. The company wasn’t sure at first what caused the sudden outage. [This map shows the times that animals caused power outages in Maine] But by 10:30 a.m., workers discovered the cause was a familiar culprit: a squirrel had snuck into the substation, causing the equipment to sense a disruption and shut down automatically, Overlock said.