Rescuers were scouring the waters off Malaysia's southern coast on Monday for 18 people missing after a boat carrying migrants from Indonesia capsized, killing one woman, a Malaysian maritime official said.
Southern Malaysian waterways, which border Indonesia and Singapore, include busy international shipping lanes and rich fishing grounds. Overloaded migrant boats also ply the waters and occasionally run into trouble.
Twenty-five people, including a woman, were rescued after the boat, believed to be carrying 44 illegal immigrants, sank early on Monday, said Abu Bakar Idris, an official of the Malaysian Maritime Enforcement Agency (MMEA).
The search for survivors began after workers on an offshore platform notified Malaysian authorities they had seen two Indonesians swimming towards them, he added.
"We have requested assistance from Singapore and Indonesian authorities to search within their own waters," Abu Bakar said in a statement.
The vessel was travelling from the Indonesian island of Batam to Tanjung Penawar in Malaysia's southern state of Johor when it sank, Abu Bakar said.
There have been several accidents in the waters between Indonesia and Malaysia.
Last June, six Indonesians went missing after a ship carrying crude oil sank off southern Malaysia, near Singapore.
In November 2016, more than half of the 101 passengers aboard died after a boat hit a reef and sank off Batam.