Earlier this week the media had reported about the incident, allegedly since late April, in which trees were axed or drilled and then filled with a white liquid which seems to be a herbicide.

They killed the thousands of trees on over 10,785 ha (26,650 acres) in Lam Ha District, 73 kilometers from Da Lat.

Planted almost 20 years ago the area was home to large pine trees with a stem diameter of 25-40cm. The forest is surrounded by local coffee farms and crops.

It was an attempt to clear land for cultivation, locals have speculated.

An area of poisoned pine forest has turned to red in Lam Dong Province.
Photo by Vietnam News Agency

On Thursday Prime Minister Nguyen Xuan Phuc told the Ministry of Public Security to "promptly find out and strictly handle the violation" and report to him before May 30.

Local authorities have started a probe to find those responsible and devise a plan to replace the trees.

The Central Highlands lost nearly 358,800 hectares (14 percent) of forests between 2008 and 2015, according to a report by the Central Highlands Steering Committee.

Most trees were chopped down by illegal loggers or cleared to make way for cash crops, roads or hydropower plants.

The country’s forests were disappearing so fast that PM Phuc ordered a total ban on clearing natural forests in 2016 to protect the remaining 2.25 million hectares.

In the three years since there has been a decline in the deforestation, but illegal logging, transportation and processing of forest products continue to occur in several locations.