Thai immigration police say more than 600 ethnic minority migrant workers from Burma have been detained while attending a traditional ceremony near Bangkok.
Police said today the ethnic Karen workers were detained Sunday at the sports grounds of the police academy in Nakhon Pathom province.
They were among at least 10,000 people who had gathered for the event. Police said they had only granted permission for a small gathering.
Thai authorities say the workers arrested could be deported to Burma.
More than 100,000 Karen are living in Thai refugee camps, having fled fighting in military-ruled Burma. The Karen National Union, which has been fighting an insurgency against the government for the last 50 years, says the army has killed civilians and burned Karen villages.