Pailin provincial authorities are searching for a suspect who allegedly commissioned the excavation of a gold mine on land the protection of which is funded by the foundation of American actress Angelina Jolie.

Provincial environmental police are holding three men at a spot where they were found guarding an excavator and 10,000 square metres of land in Boyakha commune on Sunday, said Kim Sokha, director of Pailin’s environment office.

All three said they were hired to guard the machine and area, but insisted they did not know the identity of their employer.

“Workers were illegally surrounding land near a gold mine to dig with the excavator [on protected land] near the Cambodian-Thai border,” Sokha said.

“We are searching for the person behind this illegal activity, and if we cannot find whoever is responsible for it, the excavator will be impounded at a border military police station.”

Since the questioning on Sunday, environmental police have detained the three guards at the site, Sokha said, though they have not been charged.

This is the second time Sokha’s department has cracked down on people digging or attempting to dig on the land owned by the Maddox Jolie-Pitt Foundation, run by Jolie and her husband, Brad Pitt. They started the organisation in 2003 after adopting a child from Cambodia.

At the foundation’s creation, the actress pledged an initial $1.3 million to fund protection efforts in Pailin and Battambang provinces, said Chan Socheat, its operational officer. Only two companies have been granted licences to explore the area, one of which is Vietnamese, he said.

A 1993 royal decree designated 60,000 hectares of forest land in Battambang and Pailin as a protected area, Socheat said. Since then, 20,000 hectares has been used by people who farm and live on it.