A one block radius around Polk and O'Farrell remains shut down. Investigators still do not know what caused the explosion.
PG&E crews worked mainly underground Monday to sort out the damage caused by a major fire.
"We've had crews working around the clock since the incidence began on Friday midday," PG&E spokesperson Jennifer Zerwer said. "We are working to remove cabling from underneath the ground, that's the majority of the equipment that's been damaged."
Once the cleanup is complete, crews will begin to replace the underground cable.
PG&E investigators still do not know what caused the explosion, which last Friday sent 20-foot flames shooting into the air and plumes of thick black smoke wafting through the /*Tenderloin*/. Monday it was confirmed the fumes were not toxic.
Another team worked Monday to remove drums of water presumably from underground runoff. That water will now be analyzed as well.
On Friday, close to 9,000 customers were affected by the fire. Service was rerouted and as of Monday evening, only a handful of customers were still being served by an on-site generator.
In August 2005, a similar incident occurred in downtown San Francisco, injuring a woman. Since then there have been several smaller underground explosions causing power outages. PG&E points to its aging infrastructure as part of the problem.
"We've also invested more than $200 million in the last three years alone in our infrastructure here in San Francisco," Zerwer said. "The safety and reliability of our system, the safety of our customers, as well as our employees, are our utmost priorities."