PHILADELPHIA (CBS) — City officials say the fire at the Philadelphia Energy Solutions refinery in South Philadelphia has been extinguished. The fire began after a massive explosion at the oil refinery early Friday morning.

Officials say they are continuing to monitor the air quality inside the facility every hour, so far all of the readings have come back at normal levels

The blaze had been burning ever since, as officials searched for a safe way to cut off fuel to the fire. The blaze was finally snuffed out Saturday afternoon.

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Credit: CBS3

Officials also say the gas valve that fueled the fire has been shut off and the tank involved in the explosion has been isolated.

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On Friday afternoon, officials maintained there was no threat to the public as crews monitored the air quality around the refinery. Crews will continue to monitor the air quality now that the fire has been extinguished.

“Based on the result of samples taken this morning, the health department has no findings that would suggest there is a threat to the public health as a result of today’s fire,” department director with the Office of Emergency Management Noel Feleza said Friday afternoon.

An investigation into the cause of the fire by several agencies, including the ATF,  will begin Monday morning.