Two Forest Bank prison officers have been arrested on suspicion of smuggling 'prohibited articles' into the Salford jail.
The unrelated incidents took place last month.
Both men have since been released under investigation, with police saying inquiries are ongoing.
GMP hasn't confirmed what items the guards are suspected of smuggling in, but the list of prohibited items includes tobacco, mobile phones, money and alcohol.
An HMP Forest Bank spokesperson said: "We can confirm two members of staff have been arrested.
"It would be inappropriate to comment further while a police investigation is underway."
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A Greater Manchester Police spokesperson said the arrests took place on Sunday, July 14, and Thursday, July 25.
The spokesperson added: "Two men have been arrested on suspicion of conveyancing prohibited articles into a prison.
"Both men have since been released under investigation and enquiries are ongoing.
"The two arrests are unrelated to each other."
It's the latest scandal to hit the privately-run Pendlebury prison.
As the Manchester Evening News has reported over the last two years one officer has been jailed for smuggling in mobile phones and two security guards were convicted of stealing and selling DVDs and games from the jail.
In 2017/18 more drugs were confiscated at Forest Bank than at any other prison in England and Wales, with 537 seizures made.
It was the third year in a row the prison, run by contractor Sodexo, had the highest number of seizures.
Last August Salford MP Rebecca Long Bailey described events at the prison - which houses Category B, Category C inmates and young offenders - as an example of how ‘justice on the cheap has failed’.
