Seven people, including the two crew members, were rescued and were in stable condition after drifting in the choppy waters for hours, said Lahmudin, who heads the local Disaster Management Agency.

The boat capsized in the Sipora Strait after leaving Sikakap, a town in the Mentawai Islands district in West Sumatra province, at midday, said Lahmudin, who like many Indonesians uses a single name. It was bound for the neighboring town of Tuapejat, a trip of less than two hours.

The boat was carrying 16 passengers, mostly local administration officials, and two crew members. The 11 people missing included three children and a local parliamentarian.

“Authorities are still investigating the cause of the accident, but survivors said the boat was hit by high waves in a sudden storm,” Lahmudin said.

 A rescue ship and an inflatable boat were searched for survivors with assistance from fishermen and people onshore, said Rudi, the local search and rescue agency chief who also goes by a single name.