(CNN) A large fire broke out early Friday at an oil refinery in Philadelphia, rattling the area with at least one booming explosion and lighting up the dark sky with huge balls of gas and flame.

The explosion and fire came from a vat of butane -- one of the products that come from the process of refining crude oil -- at the Philadelphia Energy Solutions refinery starting around 4 a.m., Deputy Fire Commissioner Craig Murphy said.

Murphy confirmed during an afternoon press conference that propane was also in the vat.

Social media recorded a massive fireball from the Philadelphia oil refinery early Friday.

The refinery's fire crews have been fighting the flames with city fire crews in support, and the blaze has been contained to the general vat area, Murphy said.

During the press conference, Murphy said the fire was not under control, but was "confined and contained." The fire cannot be placed under control because of the propane and butane that's burning in the vat, which is being fed by a main. Murphy said the main has to be shutdown to put out the fire, but Philadelphia Energy Solutions says they are unable to get to the valve that would shut off the main.

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