HAT YAI, Thailand -- Police have found dozens of shallow graves, a corpse and an ailing survivor at an abandoned jungle camp in an area of southern Thailand that is regularly used to smuggle Rohingya Muslims, as well as Bangladeshis and other migrants, to third countries.

An Associated Press reporter who visited the scene later Friday counted six bodies, including five that had recently been dug up. He said a rescue team told him 27 graves, each with a simple bamboo marker, had yet to be exhumed.

The grim discovery was a sharp reminder of the brutal human trafficking networks that operate in Thailand, despite repeated assurances by authorities that they are addressing the root causes.

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Acting on a tip from villagers, teams of police and rescuers were dispatched into the mountains of Padang Besar, a sub-district in Songkhla province. Reaching the camp on foot, they found a shelter with at least one corpse, said police Col. Weerasant Tharnpiem, adding that there appeared to be several other bodies as well.

Last June, the United States put Thailand in its lowest category - "Tier 3" - in its annual assessment of how governments around the world have performed in fighting human trafficking. The ranking took into account the smuggling of Myanmar's long-persecuted Rohingya community, as well as cases of migrants from neighboring countries who are forced or defrauded into working against their will in the sex industry, commercial fishing, garment production, factories and domestic work.

President Barack Obama waived invoking action under the assessment that would have allowed him to impose sanctions on Thailand, including barring imports from its lucrative seafood industry. Thailand has promised action in order to get off the blacklist, but recent revelations by the AP that its fishing vessels were treating men from Myanmar, Cambodia and Laos as virtual slaves have dented the country's reputation more.

The purpose of the camp discovered Friday - comprising small bamboo huts tucked away in the forest - was not immediately clear. But similar ones found in recent years have been used to detain Rohingya. In many cases, they paid agents for passage to what they thought would be a better life and jobs in Malaysia or points beyond. Instead, they were held for weeks, sometimes months, while smugglers extorted more money from families back home.

National police spokesman Lt. Gen. Prawut Thawornsiri said he could only confirm the discovery of one corpse, one sick man and several graves at the site.

"We are sending a team of forensic police to investigate," Prawut said in a telephone interview. "The next step is to verify their identities and nationalities. It's not clear yet who they are."

Authorities said traffickers are widely known to use the Songkhla mountains and other nearby areas for temporary camps to house Rohingya and others before smuggling them to third countries.

Rohingya Muslims have for decades suffered from state-sanctioned discrimination in Myanmar.

Attacks on the religious minority by Buddhist mobs in the last three years have sparked one of the biggest exoduses of boat people since the Vietnam War, sending 100,000 men, women and children fleeing, said Chris Lewa, director of the Arakan Project, which has monitored the movements of Rohingya for more than a decade.

Their first stop is almost always Thailand.

Instead of jungle camps, Rohingya and Bangladeshis have in recent months been taken to large ships while they wait for ransoms to be paid, said Lewa, who estimates that 7,000 to 8,000 migrants are currently parked off the coast or in nearby international waters.

Tightly confined, and with limited access to food and clean water, their health is inevitably deteriorating quickly, and increasingly there are reports of deaths, she said.

"A 15-year-old who spent two months on a boat off the coast of Thailand or Malaysia says during that time, 34 people died on three different boats," said Lewa, citing one example. "He said their bodies were thrown overboard."

Lewa believes there are only around 800 people still in jungle camps.

Conditions in the open-air pens, where they are vulnerable to rainy weather and get little food, continue to be grim. When authorities raid the camps, the sick and weak are often left behind to die, survivors have told the AP.