Managing director Mick Wilkes said an investigation into the incident was under way by the local police.
The company could confirm that the person was a male Filipino and a contractor to the company.
"At this stage, the company is unable to provide any further information pending the outcome of the investigation," he said.
Oceana Gold was arranging for counselling and support services to be available for the family and employees.
"We are deeply saddened by this very unfortunate event," Mr Wilkes said.
Oceana Gold began the tendering process to sell gold and copper concentrate from its development Didipio tenement earlier this month.
Didipio is expected to be fully commissioned by the end of 2012.
More than three years after mothballing the project after a capital expenditure blowout from $US155 million ($NZ197 million) to $US320 million in May 2008, the company is scheduled to be pouring its first concrete at the already partially developed open-pit site by November. The first mining is set for January.
Oceana Gold also operates the Macraes and Reefton gold projects in New Zealand.