The squirrel entered the substation in El Cerrito caused the outage that deprived much of the East Bay of power for two and a half hours, according to utility company PG&E.
JD Guidi, a PG&E spokesman, said the animal -- which died -- had impacted the equipment that triggered a massive power failure at 8:03 PM local time on Monday, leaving 45,000 people to be without electricity.
Power was restored around 10:30 PM. The affected cities included Berkeley, Oakland, Albany, El Cerrito, Kensington, Richmond and San Pablo, the Berkeleyside reported.