Citing the results of repeated air quality tests, Mayor Jim Kenney reiterated Tuesday that there is no lingering health threat due to Friday’s explosion and fire at a South Philadelphia refinery.

"There are no findings that would suggest a threat to public health,” the mayor said during a news conference at which he was joined by the managing director, fire commissioner, and environmental officials.

Dr. Caroline Johnson, a deputy health commissioner for the city, said experts had been carefully checking air quality for any increase in noxious chemicals and found none. On Friday, she said, tests showed very minor elevations of acetone and ethanol, but those quickly abated.

She noted that there was no evidence of any release of hydrogen fluoride, a deadly chemical used in refining. Nor, she said, was there any spike in visits to area emergency rooms for breathing problems.

Philadelphia Fire Commissioner Adam Thiel said the smoke from the blaze posed little long-term risk, saying the burning liquid petroleum gas was little different than the propane used during backyard cookouts.

Managing Director Brian Abernathy said the city had assigned a task force to explore the cause of the fire and what steps might be needed to improve safety at the complex, the largest oil refinery on the East Coast. He said the task force, which includes city officials, regulators, community members, scientists, and the refinery’s owners, would hold a hearing by the end of July.

Abernathy said Philadelphia Energy Solutions (PES), which owns the refinery, will need to be more forthcoming about what transpired. "There’s a recognition that PES is going to need to have a public conversation,” he said.

Cherice Corley, a PES spokesperson, did not return telephone calls Tuesday seeking comment. On Tuesday, the company issued a brief statement saying it had “nothing new to share regarding the incident on Friday.”

PES said it was assisting the official investigation. Once that inquiry is complete, it said, “we will share the findings.”

Once owned by Sunoco and the Carlyle Group, the refinery filed for bankruptcy in January 2018 and is now owned by its creditors. An analysis by the University of Pennsylvania later last year found the refinery remains financially shaky and could have to seek bankruptcy protection again within a few years.

Along with the task force, an array of investigators is looking into the fire. Fire marshals from the Fire Department are working with experts from the U.S. Chemical Safety and Hazard Investigation Board, the federal Bureau of Alcohol, Tobacco, Firearms, and Explosives, and the federal Occupational Safety and Health Administration.