The accident on the Penol reservoir near the town of Guatape, which is approximately 45km east of Colombia’s second largest city of Medellin, has left nine people dead and 28 others missing.
A major rescue effort involving Colombia’s air force and firefighters from nearby cities was looking for survivors at the Guatape reservoir where the four-story El Almirante boat sank.
Videos posted on social media showed motorboats coming to the aid of passengers on the upper decks as the boat rocked from side to side.
There were about 170 people on board. Overnight they reduced to 15 the number of people missing, down from an earlier count of twice that amount.
Colombian President Juan Manuel Santos, who travelled to the scene on Sunday evening, said six people had been killed, revising down an initial death toll of nine given by officials.
In the absence of a passenger list, authorities have been relying on family numbers and survivors to report their whereabouts. “What we have seen in the videos is that the boat was very close to the port… and we do not know whether it was a mechanical failure, an overloading or something to do with the currents that caused it to sink”, said Morales, the fire captain.
Some people who witnessed the tragedy from the shore said the boat appeared to be overloaded but Mr Santos said it was sailing well below capacity. None of the passengers was wearing a life vest.
Colombian rescue workers and scuba divers are continuing the search. The Antioquia regional government said on Twitter that 24 people caught in the wreck were being treated in hospital.
The reservoir surrounding the soaring rocky outcrop of El Penol is a popular weekend destination a little more than an hour from Medellin. Guatape fills with tourists on long weekends like this one, since Monday is a holiday in Colombia.