HAT YAI, Thailand - Thai police arrested three local officials and a Myanmar national they alleged on Monday were involved in trafficking and holding Rohingya Muslims for ransom at a jungle camp where 26 bodies were dug up from shallow graves last week in southern Thailand.

National police chief Gen. Somyot Poompanmoung said the suspects - including two deputy village chiefs and a municipal councillor - were believed to be part of a “transnational crime network” that included people from Thailand, Myanmar and Malaysia and had been operating for three or four years.

Friday's discovery of the clandestine camp in southern Thailand, long considered a trafficking hub for migrants seeking a better life in third countries, was a sharp reminder that little has changed despite repeated assurances by authorities that they are addressing the root causes.

It was also the latest blow to Thailand's image, following a run of disclosures about human trafficking that rights groups say is fueled by the involvement of corrupt Thai officials.

Last June, the United States put Thailand in its lowest category - Tier 3 - in an annual assessment of how governments around the world have performed in fighting human trafficking.

Thailand has promised action in order to get off the blacklist, but its reputation suffered following recent revelations by the AP that some Thai fishing vessels kept men from Myanmar, Cambodia and Laos on board as forced labour or slaves.

Somyot said police were trying to confirm reports that many more camps run by traffickers could be hidden in the mountainous jungles of southern Thailand. Police were combing Khao Kaew mountain in Songkla province, where the camp was located close to the border with Malaysia, and planned to expand their search to other areas where dense jungle obscures the land.

“We are not stopping here. We will search in the widest area and do it until we are certain that there are no other camps left,” Somyot told reporters. “We will find out if there are more.”

A lone survivor from the camp, now hospitalized with severe malnutrition, has told authorities that the smugglers had escaped earlier last week with around 100 Rohingya.

Members of the religious minority have for decades suffered from state-sanctioned discrimination in Myanmar, which is predominantly Buddhist. Mob attacks in the last three years have left up to 280 people dead, sparking one of the biggest exoduses since the Vietnam War.