It is understood the death was from a medical event.
A WorkSafe spokeswoman confirmed it was notified of the incident and were making initial inquiries.
“These inquiries will determine our next step,” the spokesperson said.
Fonterra Stirling site manager Morgan Watt says in a statement: “Sadly one of our team at our Stirling site passed away over the weekend while at work.
“It was a medical event. Our thoughts are with the family and friends, and our priority at the moment is supporting our team during this time,” Watt says.
The Stirling site is about five minutes out of Balclutha.
A police spokeswoman said in a statement: “Police were notified at 1.10am on 18 September that a person had died at that location, after suffering a medical event”.
A St John spokeswoman said it attended an incident on Mount Wallace Rd at 1.10am on Saturday and referred all other inquires to police.