(CNN) -- Thai police detained hundreds of Muslim Rohingya following a raid on a suspected people-trafficking camp, police said.
A Royal Thai Police spokesman said 531 men, women and children were detained following a raid on Sunday at a camp near the town of Sadao in the southern province of Songkhla.
Police said they were acting on media reports that Rohingya fleeing sectarian violence in Myanmar were falling into the hands of people smugglers who held them in camps, ransoming them to relatives across the border in Malaysia.
Deputy National Police Chief Chatchawan Suksomjit told the South China Morning Post that three suspected ringleaders -- all of them Thai males -- had been detained in the raid.
He said the Rohingyas were being held at an immigration detention center in Songkhla.
"We are interviewing all of them to see if they are victims of human trafficking," he said. "We have to interview them and proceed according to Thai immigration laws. It will depend on whether they want to go back.
"If they are willing, we will send them back as we have done before."
Rohingyas -- stateless Muslims from Myanmar -- have been fleeing ethnic violence in Buddhist-majority Myanmar, arriving in boats in southwestern Thailand before transiting to Malaysia where they often work illegally.
Thailand's efforts to deport Rohingya -- in some cases allegedly towing their boats back out to sea -- has come under fire from human rights groups as well as the U.S. State Department.
Phil Robertson, deputy director at Human Rights Watch, said that human trafficking had been "plaguing efforts to help the Rohingya for the last year or two at least."
"When the Rohingya boats started coming out in significant numbers circa 2009, it was very disorganized, boats were landing everywhere -- this is when the Thais were pushing them out to sea.
"But now these Rohingyas that are arriving close to the Thai coast are being seized by broker and trafficking syndicates working in collusion with Thai officials to bring these people onshore, hold them in jungle camps and then essentially ransoming them."
He said in some cases ransom money could be as much 65-70,000 Thai baht (US$2000) -- which represented a considerable amount of money for some of the world's poorest people.
"There's been a long-standing Rohingya community in Malaysia -- they have relative and friends there, there are jobs on offer."
He said that once in Malaysia, Rohingya often worked in the black economy doing dirty and dangerous jobs.
"That's where the Rohingya are headed to, that's their promised land in some ways."
Sunai Phasuk, Thailand-Burma researcher for Human Rights Watch, said that the Rohingya had the "unenviable distinction of being the most blighted" people in Myanmar.
"Denied citizenship, subject to tight restrictions on movement, employment and religious freedoms, this Muslim minority have been the target of abuses by the Burmese military for decades," he said.
"Today they face serious risks of state violence and coercion, in part arising from preparations to build a pipeline through their region that will deliver offshore gas to China. Already reports are emerging of forced relocations and other abuses tied to gas exploitation."