Underground 'boom' knocks out power in FiDi

April 22, 2011 7:39:59 PM PDT
Smoke coming from a manhole in San Francisco's Financial District caused some worries Friday afternoon. It happened at Sacramento and Davis streets.

Witnesses tell ABC7 they heard a loud boom underground, which they took to be an explosion. Nobody was hurt, but it knocked out power in the area for about half an hour.

PG&E says it cannot confirm if there was an underground fire, but insists whatever happened was not strong enough to blow the manhole cover off.