Bogota, Colombia ? A mudslide swept down on a scouting expedition in central Colombia, killing nine young hikers and leaving two others missing, authorities said Sunday.

The Colombian scouts, ranging in age from 12 to 19, were on an expedition Saturday with two guides near the snowcapped Nevado del Ruiz volcano close to their home city of Manizales, said German Salgado, regional president of the Scouting Association of Colombia.

The scouts were in a boulder-filled canyon when heavy rains caused the Chinchina river to rise several feet, sending down a crushing load of earth and rock that swept away the scouts as they were bathing and practicing knots.

“It wasn’t raining where they were,” said Maria Pilar Perez, emergency coordinator of Caldas province. “They had no idea what was coming from upstream.”