HANOI, Vietnam — A tourist boat returning from an island trip in southern Vietnam capsized on Saturday, killing 15 Indian visitors, state media reported.

The speedboat was carrying 32 Indian tourists and four crew members when it overturned about 400 meters (1,310 feet) from Hon May Rut Ngoai Island, which is near Phu Quoc, Vietnam’s largest island, authorities were quoted as saying.

Eyewitnesses told VN Express that nearby boats rushed to the scene and began pulling passengers from the water, before border guards, the navy, coast guard and other rescue agencies arrived. The rescue was difficult because many were trapped inside, VN Express reported.

Twenty-one people were rescued, and all the dead were recovered, authorities said. The injured were taken to hospitals.

Footage on Vietnamese TV showed rough seas and strong winds as rescue teams threw life buoys to people in the water. Jet skis ferried survivors back to shore while people on the beach provided first aid to victims.

Vietnamese Prime Minister Le Minh Hung ordered an investigation into the cause of the accident and directed authorities to hold those responsible accountable. He also asked authorities to review waterway and maritime safety in the area where the accident happened and other similar areas.

Indian Prime Minister Narendra Modi said the tourists were employees of a private mobile phone company taking part in an annual meeting. He wrote on social media that Indian Embassy personnel were at the scene.

Phu Quoc in the Gulf of Thailand is one of Vietnam’s most popular beach destinations. Hon May Rut island is about 10 kilometers (6 miles) south of Phu Quoc. They’re known for their white-sand beaches and clear waters and draw millions of domestic and foreign tourists each year.

The cause of the accident wasn’t immediately clear and an investigation was underway.