Kuala Lumpur: Malaysian authorities on Friday stepped up a search for survivors from a boat that sank while crammed with Indonesian migrants as the death toll rose to 15, the Malaysian coastguard said.

The count of victims increased from 14 with the recovery of another body from the Malacca Strait, while four more passengers were rescued, said Mohamad Aliyas Hamdan, a Malaysian Maritime Enforcement Agency official.

That brought the number rescued so far to 19.

Aliyas said four aircraft were now scouring seas in the area, and 12 ships have been deployed in hopes of finding more survivors.

Officials have said the overcrowded wooden vessel capsized and sank in rough seas about 16 kilometres (10 miles) off the coast of central Malaysia’s Selangor state in the pre-dawn hours Thursday morning.

‘They were leaving Malaysia to return to Indonesia,’ said Aliyas.

He said the dead included two men and 13 women.

Malaysia is Southeast Asia’s third-largest economy and a magnet for migrant workers from its poorer neighbours, with the vast majority coming from Indonesia.

About two million Indonesians are now in Malaysia working a range of low-paid jobs.

Deadly accidents in the strait are not uncommon, however, with the travellers typically attempting the crossing in rickety vessels, often at night to avoid detection.

The exact number of people on board remains unconfirmed.

Aliyas said local fishermen, who were initially on the scene and rescued some survivors, said there may have been up to 100 passengers.

Prime Minister Najib Razak issued a statement expressing his condolences.

In June 2014, more than a dozen people drowned when a boat overloaded with around 100 Indonesians sank while taking its passengers home for the Islamic fasting month of Ramadan.