Officials say one refinery worker has died after being exposed to a hazardous substance at the Valero refinery plant on Presidents Island in Memphis.

The refinery fire injured a Valero employee and a contracted worker. Two Memphis firefighters were also treated for minor exposure to the chemical mixture of propane and hydrofluoric acid.

The firefighters were exposed after performing CPR on the employees.

Memphis Fire Department spokesman Lt. Wayne Cooke says the workers were exposed to the propane and hydrofluoric acid mixture when a sight glass on a pump unit ruptured.

Firefighters were dispatched at 9 a.m. to 2385 Riverport and had the fire extinguished within 40 minutes, Lt. Cooke added.

August 2011: Two Alarm Fire at Valero Refinery
August 2011 Two alarm Fire at Valero Refinery (video)
April 2010: One Seriously Injured in Valero Fire

First responders transferred the victims to The MED's Burn Unit. One worker was in critical condition and the other in stable condition, but it was not immediately clear which plant worker died.

There have been three reported fires or hazmat situations at the Valero plant since 2010. One person was killed two others critically injured in a huge explosion at the refinery in March.

In August 2010 there was a blast inside the plant but it was brought under control about 30 minutes after it began. No one was hurt.

The cause of the fire remains under investigation.

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FOX13 News reporter Scott Madaus contributed to this report.