(KGO) A fire in an underground vault sent heavy smoke and flames out of a manhole in San Francisco's Tenderloin neighborhood for a few hours Friday afternoon, with the resulting power outage lasting well into the night.

Fire officials advised people on several blocks around Polk and O'Farrell streets to stay indoors because of the potentially toxic smoke. That advisory was lifted a few hours later, after the fire was controlled. No injuries were reported.

The intersection of Polk and O'Farrell remained closed late Friday night while PG&E crews waited for the temperature inside the vault to cool down enough for a safe investigation of what caused the fire to begin.

The fire initially knocked out power to some 8,600 PG&E customers along Van Ness Avenue, in the Western Addition and Japantown. By 10 p.m. Friday the number of customers affected was down to about 2,000, with no estimate of when power might be restored.

Firefighters had to rescue several people who got trapped in elevators when the power went out, shortly after 11:30 a.m.