Media playback is unsupported on your device Media caption Ahmed, a Rohingya, said he was caught by the Thai navy and traded to traffickers

An investigation by the BBC has revealed that Thai officials have been selling boat people from Burma to human traffickers.

Thousands of Muslim Rohingya have fled to sea in recent months after deadly communal violence in Rakhine State, with many heading east across the Andaman Sea to Thailand.

The BBC found that boats were being intercepted by the Thai navy and police, with deals then made to sell the people on to traffickers who transport them south towards Malaysia.

The Thai government say they are taking the allegations seriously and have promised to investigate.

'Canned fish'

In November Ahmed said goodbye to his wife and eight children and left western Burma.

Background: Burma unrest What sparked recent violence? The rape and murder of a young Buddhist woman in Rakhine in May set off a chain of deadly religious clashes in June and then October. Who are the Rohingyas? The United Nations describes Rohingya as a persecuted religious and linguistic minority from western Burma. The Burmese government, on the other hand, says they are relatively recent migrants from the Indian sub-continent. Neighbouring Bangladesh already hosts several hundred thousand refugees from Burma and says it cannot take any more. Q&A: Unrest in Rakhine

His fishing boat had been destroyed in clashes between Muslim Rohingya and Rakhine Buddhists, and he needed to earn a living.

With 60 others he travelled for 13 days on a flimsy wooden boat across the Andaman Sea to the coast of Thailand.

When they were caught by the Thai navy not far from shore Ahmed thought his ordeal was over. In fact it had just begun.

That night the Rohingya were taken from the border town of Ranong in a police van. After two hours they were bundled out and put in the back of six smaller vehicles and hidden under nets.

"We were forced to lay down next to each other just like canned fish," he said.

Ahmed did not know it at the time but a trade had taken place. The 61 Rohingya were now heading south towards Malaysia in the custody of people-smugglers.

When they got out of the vehicles they were prisoners in Su Ngai Kolok, a town on the Thai Malaysia border.

"They dug a hole for us to use as a toilet. We ate, slept and excreted in the same place," he said. "The smell was horrible. I was poked with an iron and beaten with a chain."

Image caption Ahmed's back is scarred from the beatings he received

The traffickers had paid money for the Rohingya and were determined to get their money back. Ahmed and the other Rohingya were periodically given a phone to call friends and family to beg for help.

"The broker said that they bought us from police," he said. "If we don't give them money they won't let us go. They said: 'We don't care if you die here'."

The price for Ahmed's life was set at 40,000 Thai Baht, about $1,300 (£820) - a substantial amount for an ex-fisherman. Ahmed called his wife and instructed her to sell a cow. But that only raised half the amount.

After a month as a captive, as he began to despair a fellow Rohingya in Thailand came to his rescue and loaned him the rest.

Ahmed was set free and put on a bus back north to Phuket. Despite all that happened to him, he is surprisingly calm about his treatment by Thai officials.

"I'm not angry at the navy. I don't hold any anger or grudge with me anymore. I'm so grateful that I'm alive," he said.

'Natural solution'

With weather conditions favourable Rohingya boats are now arriving on the Thai coast almost everyday. And Ahmed is not the only one being sold by Thai officials.

Image caption Whole families are trying to escape the communal violence in western Burma

We took a close look at the fate of one particular boat which arrived on New Year's Day off the holiday island of Phuket.

On 2 January the 73 men, women and children were brought onshore, put in trucks and it was announced that they were being driven to the Thai/Burma border crossing at Ranong and deported.

But they did not get that far. A deal had been struck to sell the Rohingya to people smugglers.

When the trucks reached the town of Kuraburi, the Rohingya were transferred back into a boat and pushed back out to sea.

We spoke to one of the brokers involved in the deal. They said that 1.5 million baht (about $50,000, £31,500) had been transferred from Malaysia and paid to officials in Thailand. That amount was confirmed to us by other members of the Rohingya community in Thailand.

The Thai authorities told us they believe there are just a few corrupt officials. But in the border town of Ranong a Thai official closely linked with the Rohingya issue told us that working with the brokers was now regarded as the "natural" solution.

With the Rohingya denied Burmese citizenship, deportation is fraught with difficulties.

Image caption Thailand considers the Rohingya to be economic migrants

Thailand in turn does not want to encourage people that it considers to be almost almost exclusively economic migrants.

"The Rohingya want to go Malaysia and Malaysia accepts these people because they are Muslims too," the official said. "No matter what they will try and go there, the question is how they get there."

Malaysia has allowed the United Nations Refugee Agency to assess Rohingya claims for asylum. Thailand does not, reserving the right to determine for itself who it considers to be a refugee.

'Systematic solution'

We took our information to the Thai foreign ministry. Permanent Secretary Sihasak Puangketkaew told us an investigation was underway.

"We cannot at this moment conclude who these perpetrators are but the Thai government is determined to get to the bottom of the problem," he said.

"At the same time the Thai government is doing its best to take care of these people on the basis of humanitarian principles.

"At the same time we feel very strongly that all of us will have to work together through international co-operation to see how we can put on place a durable and systematic solution."

There have been influxes of Rohingya before and in 2009 the Thai government was heavily criticised for its policy of towing boats back out to sea.

Those boats were almost exclusively male and the Thai government said they were economic migrants. This time it is different.

Ethnic clashes in western Burma have forced more than 100,000 Rohingya into camps and for the first time the boats crossing the Andaman Sea are a mix of men, women and children.