Thiel said crews have neutralized the largest quantity of hydrofluoric acid on site. The work reduces the risk to the community but doesn't eliminate it.
Efforts to fully clean up and close the refinery will take longer, he said.
Viewer Videos show Philadelphia refinery explosions
"Continuing to do a safe operation. Again, that's our primary concern, which is one of the reasons these things are slow," he said. "We're always putting those incident priorities top of mind: life, safety, property, protection and environmental conservation."
The blaze at the Philadelphia Energy Solutions refining complex on Passyunk Avenue in South Philly broke out around 4 a.m. on June 21, at a tank containing a mixture of butane and propane. Five workers were treated for minor injuries, and nearby residents were asked to stay inside.
At the height of the response, the fire grew to three alarms. There were more than 120 firefighters on the ground with more than 50 pieces of equipment, and area neighbors were told to shelter in place.
Firefighters will remain on scene until the situation is under control and the investigation is complete.
Concerned residents can call the PES Community Information Hotline at 215-339-7300 for updates and the status of the refining complex. PES also set up a number for residents to report damage from the incident: 800-899-1844.