The indigenous workers of the UPDF were detained on suspicion from a community centre in Panchlaish in the city.

A three-member police probe committee after interrogating the UPDF men found they were not involved in any illegal activities, sources said.

UPDF sources said their workers gathered at the community centre to chalk out programmes on the occasion of Baisabi -- a traditional festival of the tribal people of Chittagong Hill Tracts -- next month.