An investigation is underway after three workers suffered chemical burns at Alcoa's alumina refinery in Pinjarra.
Emergency crews, including multiple ambulances, were called to the refinery around 5.20pm on Tuesday.
An Alcoa spokeswoman said the men's burns were a result of a valve failure.
"A valve failure at Alcoa’s Pinjarra Alumina Refinery resulted in three employees being exposed to process material,” the spokeswoman said.
Two of the men had to be airlifted to Fiona Stanley Hospital due to the severity of their burns while the third man was treated at the refinery.
It is understood the chemical was sodium hydroxide, also known as caustic soda.
“The area in question has been isolated and clean-up of the material has commenced," the spokeswoman said.
“An investigation into the cause of the incident is underway and the Department of Mines, Industry Regulation and Safety has been notified.”
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