OAKLAND -- An apparent problem with a circuit breaker Tuesday morning led to a power outage affecting almost 11,000 PG&E customers in the hills areas near Highway 24 to Montclair and parts of Rockridge, officials said.

The outage happened at 10:13 a.m. and power was restored to all 10,783 customers by 10:30 a.m. a PGE spokeswoman said.

The problem occurred at a PGE substation near the Caldecott Tunnel and appeared to be related to a circuit breaker, the spokeswoman said.

What caused the malfunction was under investigation.