Banteay Meanchey provincial police yesterday said they had already begun gathering evidence in their investigation into a Poipet Town riot on Monday that left three protesters and a security guard injured, as local group Adhoc released a statement accusing the authorities of violating the rights of striking porters.

Provincial police chief Ath Khem said yesterday that while the investigation was under way, it remained unclear what factors instigated the riot.

“Now some of our police officials are beginning to investigate, but we have not yet found who is behind inciting the protesters to do a violent protest,” he said, adding that, “however, we have collected some evidence”.

Monday’s demonstration saw some 100 cross-border porters gather in front of the Poipet Town offices of the Customs and Excise Department, blocking traffic with their carts and demanding that taxes on goods imported from Thailand be lowered.

Police and protesters clashed at the standoff, with one protester being badly beaten and ultimately hospitalised. The rest of the demonstrators then began burning tyres in the street and pelting security forces and the Customs Department with stones, injuring one security guard and smashing much of the office building’s glass façade.

Ny Chakrya, chief investigator for Adhoc, yesterday laid the blame for the outbreak of violence at the feet of authorities, accusing them of exacerbating the situation.

“Our staff observed and saw that the police and military police used violence against the cart workers first,” he said, adding that authorities “must accept responsibility in this case”.