More than a dozen visitors were banned from entering a prison in Doncaster after failing drugs tests.
Police carried out checks at HMP Lindholme yesterday as part of a crackdown on illicit items being smuggled into the jail.
Thirteen visitors were turned away after positive tests for drugs either on their person or in their vehicle.
A 24-year-old man from Nottingham was also arrested on suspicion of attempting to smuggle banned items into prison, and an investigation is underway.
Two people were prosecuted for driving without insurance and had their vehicles seized.
The operation was carried out by members of South Yorkshire Police's Fortify team, which targets organised crime gangs.
Detective Inspector Steve Smith said: “We’ve been working in partnership with the prisons in the Doncaster area for a significant period of time now and the message we’re sending to both inmates and their visitors is simple.
"We know how important the contact you have during visiting time is. Please don’t risk having this privilege taken away by thinking that you can outsmart the system.You can’t.
"If you attempt to bring illicit items into a prison they will be found, and you will be arrested and possibly charged.”