Police investigate after worker finds ‘poison’ in lunch at Pilbara mining site

A police investigation into possible attempted poisoning is underway after a worker at a remote mining company construction site in Western Australia noticed a bad taste as he started eating a meal.

The contractor employee also noticed discolouring in a piece of fruit he was served on Monday at the dining hall at the Pilbara site run by mining magnate Gina Rinehart's Roy Hill company.

He alerted staff who contacted police.

Analysis of the food item confirmed the presence of a dangerous chemical late on Wednesday, but it appears to be an isolated incident, with no similar reports since, police said.

It is not known what the intent of the poison was, or if there was a specific target.

Major crime squad detectives are investigating.

A statement from Roy Hill company said the employee had been tested and had shown no signs of health issues and there had been no other reports of contamination.

"Our first and foremost priority is the safety and wellbeing of our people," said Roy Hill Chief Executive Officer Barry Fitzgerald.

"We have tightened our food security as a means of ensuring no further incidents occur and are working closely with the police in their investigation."