After a flight from Mitu, the C-46 arrived near Villavicencio at about 16:30 LT. The crew were cleared for a circling approach to runway 04. Weather was poor at the time of the approach. There was heavy rain with a visibility of 1000 m. After passing the Missed Approach Point the crew did not see the runway and began to manoeuvre in the area in order to obtain visual contact with the runway. The airplane wandered over mountainous terrain until it struck the side of a hill and crashed. PROBABLE CAUSE: Human factor in operational decisions involving the loss of situational awareness of the crew, departing from the standard approach procedures, in this case (VOR-DME, NDB Rwy 04/22,) to find the runway that is very close to the mountain range in low visibility conditions. CONTRIBUTING FACTORS: Restricted visibility of the VOR at the runway and locally, mainly at the 22 treshold and to the NNE.