Forensic investigators found the victims in the northern province of La Guajira after a tip from former collaborators of the United Self Defence Forces of Colombia (AUC), a right-wing group that recently demobilised in a peace agreement with the government.
An estimated 10,000 people were killed in the last two decades by right-wing fighters, according to recent figures from a panel for victims' rights created by the government.
AUC completed the demobilisation of 31,000 fighters in April as part of an agreement with the government. Under the pact, paramilitary fighters face maximum eight-year prison sentences if they confess their crimes and help compensate victims' families.
Paramilitary groups were formed by wealthy landowners, drug traffickers and plantation owners in the 1980s to combat left-wing guerrillas who have fought the government since 1964.