A major power outage swept across San Francisco on Saturday, leaving up to 130,000 customers without electricity, disrupting traffic and forcing some businesses to close temporarily, officials said.

Large parts of the city were affected, according to the Department of Emergency Management and utility officials. Authorities urged residents to call 9-1-1 only for life-threatening emergencies, avoid non-essential travel and treat non-functioning traffic lights as four-way stops.

City officials also issued safety guidance during the outage, advising residents to keep refrigerator and freezer doors closed, turn off major appliances to prevent power surges and avoid using gas stoves, grills or generators indoors because of the risk of carbon monoxide poisoning.

Traffic congestion was reported in several neighbourhoods as traffic signals went dark, while some shops and services suspended operations because of the lack of power.

The utility Pacific Gas and Electric Company said the outage affected around 130,000 customers at its peak. Crews were working alongside first responders and city officials to restore electricity as quickly and safely as possible.

Later updates indicated that power had been restored to many areas of the city, though about 40,000 customers were expected to remain without electricity overnight.

Officials continued to stress safety precautions, encouraging residents to check on neighbours, particularly older people and those with medical needs, as restoration efforts continued.

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