A massive search operation was underway Monday for a Colombian army general whose surprise capture by leftist rebels prompted President Juan Manuel Santos to suspend 2-year-old peace talks.

Gen. Ruben Dario Alzate was surveying a rural energy project along the remote Atrato River in western Colombia when he and two others were snatched Sunday by armed men. A soldier who managed to flee in the group’s boat said the kidnappers belonged to the 34th front of the Revolutionary Armed Forces of Colombia, or FARC.