A long term power cut took place to downtown business and homes in San Francisco on Friday due to equipment failure at autility station and a subsequent fire pulled the plug on.

An outage that began late on Friday morning and continued into the afternoon cut power to about 88,000 customers in the busy heart of the city, according to PacificGas and Electric spokesman Paul Doherty.

"We deeply apologize for the inconvenience this has caused around the city," Doherty told AFP.

"We know it was an equipment failure. It is premature tospeculate on a specific cause," he said, while discussing the cause of the fire.

Traffic lights were out of service and shops plunged into darkness. But many people seemed to take the outage in stride, leaving offices or apartments to socialise on streets where traffic was more subdued than on typical work days.

Some cafes or shops continued to serve customers, with people using cash or mobile payment services such as Squarethat let credit or debit cards be processed through smartphones or tablets.

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Public transit operator BART temporarily closed its underground metro station in the city center.

 Fire fighters said on Twitter that they received more than 100 calls, 20 of them related to people trapped in elevators. By shortly after 4 pm (local time), electricity had beenrestored to all but approximately 3,000 customers, PG & Espokes woman Andrea Menniti said in a message on Twitter. The bulk of the outage lasted about seven hours.

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