PHILADELPHIA (CBS) — A briefing was held Thursday on the cleanup process at the site of the Philadelphia Energy Solutions fire. The refinery used hydrofluoric acid, an extremely dangerous industrial chemical.

Tens of thousands of gallons of the acid will have to be neutralized before the site can be declared safe and that process is now underway.

Philadelphia Fire Department Commissioner Adam Thiel says since the June fire and explosion, he feels like the hazard has been reduced to the point where the fire department and Office of Emergency Management do not need to have a continual onsite presence.

Monitoring systems are still being used around the clock.

For more stories on the PES refinery explosion, click here.