A boat carrying about 100 people capsized off the western coast of Malaysia on Thursday, maritime authorities said, and media said it was carrying illegal immigrants.
A spokesman for the Malaysian Maritime Enforcement Agency said it was not immediately clear if there were any casualties, but that several survivors had been rescued by fishermen.
Southeast Asian nations in the summer faced a huge migrant crisis, with more than 4,000 landing in Indonesia, Malaysia, Thailand, Myanmar and Bangladesh since Thailand launched a crackdown on people-smuggling gangs in May.
But no such boats have been reported in recent weeks.
The accident happened as Europe faces its biggest refugee crisis since World War Two and has yet to find a common response. Thousands of people from the Middle East, Asia and Africa have died making the journey across the Mediterranean and on land in Europe.