Malaysian police said 13 bodies, believed to be Indonesian migrants, were found washed ashore after their boat capsized in bad sea conditions.
The bodies of four men and nine women were discovered on a beach in southern Johor state by members of the public early on Tuesday, Rahmat Othman, the district police chief, said.
Authorities found an overturned wooden boat not far from the beach, which had probably capsized before dawn.
Rahmat said that the boat was believed to be carrying 30 to 35 people, most probably Indonesians trying to sneak into the country.
A search-and-rescue operation was under way but was hampered by high tides and choppy seas, he said.
Such tragedies are not uncommon in Malaysia. Many Indonesians are willing to risk their lives by travelling on boats believed to be old and unsafe to work in Malaysia illegally, or to return to their hometowns.