A man has died while clearing a slip on the Milford Road in Fiordland.
St John says the 65-year-old worker sustained severe head injuries in the accident, which involved a compressed air hose.
St John communications spokesperson Alana Lynch says ambulance staff were flown to the site in a rescue helicopter.
They treated the man before he died just before 1pm on Friday afternoon.
Ms Lynch says another person on the site performed CPR before they arrived.
Police in Te Anau say the man worked for a contractor.
Sergeant Tod Hollebon says two other workers received minor injuries and were treated at the scene.
Mr Hollebon says health and safety officialsare heading to the site to investigate, along with a safety representative from the contractor.
He says police will also investigate on behalf of the coroner.