A prison worker has been arrested on suspicion of possession with intent to supply Class A drugs.
The woman, who is in her thirties, was also arrested on suspicion of misconduct in a public office at HMP Hindley in Wigan, Greater Manchester Police said.
Parts of the prison and a vehicle were searched and amounts of suspected Class A and Class B drugs recovered, police added.
The arrest follows a joint operation between Her Majesty's Prison and Probation Service and Titan (North West Regional Organised Crime Unit) into corruption in prisons across the North West of England.
A police spokesperson said: "This morning a woman in her thirties was arrested on suspicion of possession with intent to supply Class A and Class B drugs.
"She was also arrested on suspicion of misconduct in a public office at HMP Hindley in Wigan.
"The woman remains in custody for questioning."
Detective Sergeant John Davies, of Titan's Prison Investigation Unit, said: "This arrest follows a three-month investigation into corruption within prisons across the North West and has only been made possible with the support of staff at HMP Hindley.
"While we have made an arrest, I must stress that our investigation does not stop here and we will continue with our inquiries."
Stuart Nicholson, security governor at HMP Hindley, said: "Corruption of any kind will never be tolerated in our prisons.
"This arrest forms part of an ongoing investigation and we will continue to work with Titan and help them with their inquiries."
