Spare keys to 180 cells in Belgium's Leuven prison went missing a week ago, raising fears one of the inmates may have laid hands on them, the daily Het Laatste Nieuws said Wednesday.

Staff have been quietly on the lookout for the prison chaplain's keys since last Thursday, one being a pass-key to 180 cells and another to the doors separating the jail's 20 sections.

"Whoever has it can go anywhere within the prison walls," said a guard quoted by the paper.

Management has no clue as to whether the keys were lost or stolen and at first appeared to have kept quiet about the incident. Several locks are currently being changed however, the newspaper said.