The boat was carrying dozens of refugees from Myanmar’s persecuted Rohingya Muslim minority when it sank.

Authorities in Malaysia and Thailand have recovered at least 21 bodies as they search for survivors after a boat carrying Rohingya refugees fleeing Myanmar sank, police and maritime officials said on Monday.

Officials said the boat was carrying about 70 migrants when it capsized near Thailand’s Ko Tarutao island, just north of Malaysia’s Langkawi Island, three days after departing from Myanmar’s Rakhine state.

They were believed to have been part of a larger group of some 300 people who were split between at least two boats, police said.

Tarutao is just north of Malaysia’s island resort of Langkawi, where officials said search-and-rescue operations were being concentrated.

Thirteen survivors have been rescued in Malaysian waters since Saturday, the Malaysian Maritime Enforcement Agency (MMEA) told reporters on Monday.

Search-and-rescue operations were expected to last for seven days, Romli Mustafa, MMEA director in the northern states of Kedah and Perlis, told reporters on Monday evening.

Hundreds of Rohingya people boarded a vessel bound for Malaysia two weeks ago and were transferred onto two boats on Thursday, Malaysian authorities said.

One boat carrying 70 people sank shortly afterwards, while the fate of about 230 people on board the other vessel remains unclear, officials said.

More than 5,100 Rohingya boarded boats to leave Myanmar and Bangladesh between January and early November of this year, and nearly 600 of them have been reported dead or missing, according to data from the United Nations Refugee Agency.

For years, many Rohingya have embarked on rickety wooden boats to try to reach neighbouring countries, including Muslim-majority Malaysia and Indonesia, as well as Thailand, bidding to flee persecution in Myanmar or overcrowded refugee camps in Bangladesh.

Buddhist-majority Myanmar denies abuses against the Rohingya in Rakhine state in the country’s west, but claims the minority are not citizens but undocumented immigrants from South Asia.