Thai authorities have rounded up more than 800 Rohingya Muslims in separate raids over the past week with the government accusing human traffickers of exacerbating the growing wave of refugees fleeing violence-stricken Myanmar.

Police and government officials found nearly 400 Rohingyas – including 230 men, 31 women, 22 boys and 24 girls – in southern Thailand on Thursday and around 307 asylum seekers in a raid in the same district on Friday. The government said they will be sent back to Myanmar, according to AP.

In a third raid on Sunday, 140 people were detained, including 74 children.

An initial investigation into Thursday’s raid revealed the refugees had been held at the location for nearly three months and were sold for 60,000 to 70,000 baht ($1,975 to $2,304) per person.

Police arrested eight suspects involved in the raid and face charges of transporting and sheltering illegal migrants.

Human rights groups have urged the Thai government not to deport the Rohingyas back to Myanmar, where they may face persecution, and instead allow the UN High Commissioner for Refugees to screen them.

“Thailand should scrap its inhuman policy of summarily deporting the Rohingya, who have been brutally persecuted in Burma … Until UNHCR is allowed to conduct refugee screening, the Thai government should halt forcible returns of the Rohingya,” Human Rights Watch said.

Transporting refugees from Myanmar has become a big business for smugglers. This causes serious problems for Thailand which could face US sanctions if it fails to curb human trafficking through the country.