A tourist boat packed with about 160 passengers for the holiday weekend capsized Sunday on a reservoir near the Colombian city of Medellin, leaving at least six people dead and 31 missing, officials said.

Rescuers including firefighters and air force pilots in helicopters searched for survivors at the Guatape reservoir where El Almirante ferry sank. A flotilla of recreational boats and jet skis rushed to the scene, pulling people from the boat as it went down and avoiding an even deadlier tragedy.

Police commander Jorge Nieto told Blu Radio that authorities were still in the process of identifying the victims. The majority of passengers were believed to have been Colombian.

Margarita Moncada, the head of the disaster response agency in Antioquia state, earlier put the number of dead at nine people, with 28 missing.