West Yorkshire Police arrested four men this week as part of a joint operation with the HM Prison Service to clamp down on drugs being smuggled into jails.
On Sunday and Thursday, visitors who went to see inmates at HM Youth Offenders Institute in Wetherby and HMP Wealstun were searched.
During the operations, 57 vehicles and 75 people were stopped and searched as they arrived for visits.
Four arrests were made in total.
A 38-year-old man from Leicester was arrested and cautioned for possessing Cannabis.
A 17-year-old boy from the Scunthorpe area was arrested and subsequently charged with conveying a prohibited article - tobacco - into prison.
Two men aged 50 and 24 were arrested on suspicion of possessing Class B drugs and have been bailed.
Eleven fixed penalty notices were issued for driving and document offences while two vehicles were seized.
A force spokesman said the operation was intended to disrupt the supply of drugs into the prison and to rehabilitate drugs users.
Inspector Vijay Singh of the Force’s Drugs and Offender Management Unit, said: “Drugs supply into prisons not only undermines the efforts of drugs workers, who aim to help users to break the cycle of drugs and crime, but it also impacts on the wider community if people continue to offend on release to feed their addictions.
“Attempting to smuggle drugs or other contraband, such as mobile phones, into prison is a serious offence that carries severe penalties – a lengthy prison sentence in most cases.”