Four hazmat crews were dispatched to 3000 Penrose Avenue to treat workers who had been exposed to vapors.
A total of 10 people have been transported to local hospitals - 7 to Methodist Hospital and 3 to the Hospital of the University of Pennsylvania. All are in stable condition.
Authorities are still trying to determine what caused the release.
Sunoco released a statement saying the incident was contained to the refinery and that there was no impact outside of the plant.
Hydrofluoric acid is a hazardous liquid and vapor which can cause severe burns, which may not be immediately painful or visible. It may also be fatal if swallowed or inhaled.
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