UPDATE 10.31am: A Loddon Prison inmate is being charged with criminal damages by fire, after he set alight a cardboard box in his cell at 7.35am.
A Castlemaine police spokesman said a bed was damaged by the fire and the cell was damaged by water putting out it out.
He said the fire only lasted for a "couple of minutes" and no one was injured.
He could not confirm how the inmate got hold of the matches.
EARLIER: A small fire broke out at Loddon Prison this morning, after a cardboard box was set alight in an inmate's cell.
Four CFA units attended the fire and it has since been put out.