Colombian officials say at least six people are dead and 31 missing after a four-story ferryboat with about 170 passengers capsized on the Penol-Guatape reservoir, a popular tourist destination near city of Medellin, Sunday.

Speaking to reporters at the reservoir, the head of disaster relief for Antioquia province, Margarita Moncada, said that 99 people were rescued and 40 others managed to swim to safety by themselves.

WATCH: Social media video of boat capsizing

​

Recreational boats and jet skis rushed to the scene, pulling people from the boat as it was sinking.

Rescue teams, including air force pilots and firefighters were searching for survivors at the reservoir, where the Almirante ferry sank.

Visiting the scene of the accident, President Juan Manuel Santos said the boat did not appear to be overloaded.

The cause of the accident is unclear.  Some survivors said they heard a loud noise just before the boat began to sink.

Monday is a holiday in Colombia so the reservoir and nearby town were more crowded than usual.
…