At least six people have died after a boat sank in a reservoir in north-west Colombia near Guatape, according to officials.
The passenger boat had four decks and around 170 tourists were on board at the time of the incident, according to the BBC.
A witness said that the vessel sank in less than five minutes.
When people on nearby leisure boats saw what had happened they quickly rescued stricken passengers from the water and saved some of those on the top deck.
Officials say 133 people were rescued. Sixteen others, however, are still missing. Twenty people have been taken to hospital, while divers and army helicopters search for survivors.
Some of those rescued have said they were not given life jackets for the boat trip.
Fire service captain Luis Bernardo Morales said: "We do not know whether it was a mechanical failure, an overloading or something to do with the currents that caused it to sink," according to the AFP news agency.
Residents local to the area claim that the boat had sunk before but had undergone repairs to enable further use.