At least 10 foreign tourists and five Indonesian crew are missing after a boat sank off the coast of eastern Indonesia, the BBC news reported.
Ten people were rescued after the boat foundered off Sumbawa, between Lombok and the Komodo Islands.
A representative of the tour company operating the boat said it was likely to have encountered stormy weather.
The UK Foreign Office says two British nationals have been hospitalised following the incident. It would not comment on the nature of their injuries.
Lombok, which is next to the resort island of Bali, attracts thousands of tourists each year.
A search and rescue official in Lombok has told the BBC that the 10 survivors are tourists from the UK, New Zealand, Spain, France, Germany and the Netherlands.
Officials said the boat sank early on Saturday but the survivors were not rescued until late that day.
"The incident took place... when the boat hit a reef and sank", an official said.
"Fishermen managed to rescue five of them alive later at night on Saturday, and five other foreigners were rescued by a sailing boat".
Accidents at sea have frequently occurred when migrant boats navigate through the archipelago, but accidents involving tourist boats are rare.