Up to 20 juvenile offenders who "pelted" prison workers with projectiles, listing the re-election of US President Barack Obama among other demands, face charges over a night-long riot that forced many workers into hiding at a north Queensland youth jail.

Police still did not know why the prisoners, who were playing football on the oval when an incident elsewhere in the Townsville facility diverted staff attention, began damaging the prison and assaulting staff, gaining "free rein" over the centre on Thursday night.

Some of the offenders climbed on a roof and began demanding KFC, drugs and alcohol, reportedly refusing to come down unless Mr Obama was re-elected US president for an unconstitutional third term.

Northern Police Region Assistant Commissioner Paul Taylor said 29 staff were forced to seek refuge in the Cleveland Youth Detention Centre's visitor centre, with four injured.