I used to live next door to a couple of whom the husband was a Bail Hostel Manager. He often had to supervise prisoners from his hostel out on bail in his large minibus while they performed various tasks such as litter-picking and street-sweeping. They seemed to have an endless supply of drugs, knives, mobile phones (not allowed) and so on. During the nights, the place was chaotic with prostitutes being smuggled in, drug-dealers hanging about outside and fights breaking out at all hours.
If prisoners are working in 'gangs' out in the fields or inside factories, imagine the security risks and potential dangers.