About 4,300 customers in York Township were left without power Thursday morning when a tree limb fell on Met-Ed power lines, company spokeswoman Kathy Seilhamer said.
Power was lost about 5:45 a.m., and the tree limb caused a breaker to open at a substation, creating smoke, she said.
"It was not a transformer fire," Seilhamer said.
Crews rerouted electricity to all but about 2,300 customers by 7:30 a.m., she said.
Workers were clearing the tree limb, and power was expected to be restored to all customers by 9:30 a.m., she said.