About 15,000 Island residents lost power for 12 minutes this morning.
The outage area was on the main island, from Sherman Avenue east, and on all of Bay Farm Island.
The power went out at 7:33 a.m. and was restored by 7:45 a.m.
As of 8:30 a.m., the cause of the outage was still unknown, according to's Bill Garvine. "Fortunately we had all the crews here, they start at 7 a.m," said Garvine. "So they are out looking for the source."
The outage triggered the emergency warning system to sound on Bay Farm Island — though the siren (usually reserved for noon on the first Wednesday of each month) was also heard on the east end of the main island.
"We're not really sure what happened yet," said an dispatcher. "We think that it may have been related to the power outage, but they were not set off by the police department."
As of Tuesday morning, the cause of the outage is still unknown.
Someone saw a large spark on Clement Avenue, where one of the main lines that brings power onto the Island runs, said Garvine.
An Alameda Patch Facebook commenter noted this: "I heard something loud from Clement's direction near Oak as my power dimmed then failed. I thought one of the transformers in our neighborhood burnt out!"
After the system shut down because of a fault, likely caused by an animal or a truck backing into a power line or some other small incident, power was restored, said Garvine, by switching the load from the disrupted portion of the grid to another substation.
"We have two substations, each of which is capable, for awhile, of carrying the entire load in Alameda and it takes time to make that switch," he said. This morning, making that switch took 12 minutes.