At least three senior officials of the National Land Commission (NLC) are set to be questioned over the killing of American Esmond Bradley Martin.
Mr Martin was investigating illegal trade in ivory and rhino horns. He was murdered at his Karen home in February.
Detectives said NLC officials tried to aid the transfer of Martin’s 20 acres to other parties.
Martin, 75, was the third owner of the land that originally belonged to scouting movement founder Robert Powell, popularly known as Lord Baden Powell. Baden Powell sold the land to another man who later transferred it to Martin.
One suspect has been arrested over the killing.
The suspect is said to have sent a text message to Martin, detailing the LR number of his land, days before his killing.
“The suspect sent the LR number to the slain man’s mobile phone. He had also got in touch with him, saying the land was his,” said an investigator.
It has since emerged that the same suspect was in touch with NLC officials and had tried to change the ownership details of the land.
It is on the basis of this evidence that detectives have summoned the NLC officials to give their side of the story.
This emerged after the police stumbled on documents showing the alleged grabbers had tried to change ownership of the 20-acre piece of land.
The same people had been in constant communication with one of Martin's employees prior to his death.
“We believe these people targeted his land and his elimination was the surest way of dealing with the matter,” said an investigator.
Martin was found dead on the floor of his house on February 4, with a stab wound in the neck.
The detectives said they had so far found a link between the suspected grabbers and possible killers as well as the worker who they believe was used to commit the offence.
The officers believe the person behind the killing knew the compound well and Martin's dogs were familiar with him or her.
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