BBC News | ASIA-PACIFIC | Cyanide seeps into PNG rivers

There are no reports of casualties, but the country's National Disaster and Emergency Service has issued emergency health warnings to villagers in the affected area, urging them not to drink the river water.

Investigation

Authorities are preparing to investigate how a crate of the deadly chemical fell from a helicopter into the jungle while being transported to the Tolukuma gold mine.

According to the US National Academy of Sciences, exposure to between 50 and 150 milligrams of cyanide can cause immediate death.

And Professor Kirpal Singh of the University of Papua New Guinea voiced concerns that native tribes in the region could suffer.

"People using this water are likely to die - they cannot survive," he said.

However, Dome Resources played down those fears, with managing director Michael Silver saying that the rivers would dilute the cyanide, so preventing any threat to villagers downstream or to wildlife.

Romanian incident

The company's decontamination team has collected all visible cyanide pellets and put them into sealed containers, which are being transported to the mine.