The group, which consisted of 12 musicians and eight crew members, disappeared in Nuevo Leon, Mexico, after playing for a private party in Hidalgo, El Universal reported.
The mass grave was found in the township about 30 miles from the site of the party, the newspaper reported Monday.
Authorities said the victims had been dead for about 36 hours, putting their time of death at just after the private show.
Searchers looked for the other 12 band members.
Kombo Kolombia is a Colombian-style band that has produced hits such as "I Want To Fly," "Back" and "Only You Make Me Happy," the news report said.