Villagers have been digging for precious stones in Pailin province on the sites of old gem mines abandoned by Thai companies in the 1990s.
The firms were given concessions to mine the areas in Sala Krau district by Khmer Rouge leaders who needed income to pay their troops.
The firms stripped the land of gems and returned to Thailand after Khmer Rouge rebels defected to the government in 1996.
Provincial deputy governor Sar Moniroth said her province was once rich in gems but no longer had many left, while most people made a living from growing vegetables and rice.
However, groups of low-income families recently attempted to revive small-scale gem mining on the sites of the old excavation pits.
“They saw stones glinting in the night on the land and flocked to find gems,” Ms Moniroth said.
“There are still some precious stones, but not many now.”
Photos in local media showed villagers digging for gems and sifting through the dirt at base of a mountain in Sala Krau district’s Stung Kach commune.
Commune police chief Chum Voeun said the people were looking for rubies and other precious stones.
“They were digging for gems near their homes because the farming season is over,” Mr Voeun said.
Pailin province was a Khmer Rouge stronghold between 1979 and 1996.