Three staff members working at an East Staffordshire prison are being investigated by the police for allegedly having "inappropriate relationships" with inmates.
A prison officer, a nurse and another member of staff at HMP Dovegate have been arrested on suspicion of misconduct in a public office, according to a spokesman from Serco, the company which runs the jail.
Another healthcare assistant facing similar allegations was sacked when an internal investigation found she had "not followed procedures", he said.
And one of the staff under investigation - who is alleged to have had relationships with "one or more prisoners" - is also suspected of trafficking illicit items into the Category B jail, said the spokesman.
The nurse and healthcare assistant worked at Care UK, which is contracted by Serco to provide medical services at the prison, in Marchington.
The prison officer and other member of staff are employed by Serco, the private firm paid by taxpayers to run Dovegate.
John Hewitson, Serco contract director for HMP Dovegate, said: "We expect the highest standards of behaviour from prison officers and we will not tolerate inappropriate relationships or conveying contraband into the prison.
"We will not hesitate to inform the police if we suspect any such activity and if appropriate we will seek prosecution of any individuals involved."
A Care UK spokesman said in response: "We take all allegations of inappropriate relationships between staff and prisoners very seriously and always conduct a thorough internal review into the circumstances leading up to those allegations.
"Last year we reviewed two allegations of inappropriate relationships between staff and prisoners.
"In the first case, the prison service revoked security clearance and the person was dismissed from their position with us.
"In the second case, the prison service informed us about an [alleged] inappropriate relationship involving a staff member who had already resigned their position and left Care UK.
"As a part of our internal review we referred that person to the Nursing and Midwifery Council and we understand they were also questioned by the police.
"However, we are unable to comment further due to it being investigated solely as a police matter."
The nurse whose security clearance was revoked was dismissed from Care UK in June, but did not face police action.
The other former Care UK worker was arrested in November.
The two Serco staff members were arrested in January.
A Staffordshire Police spokesman said: "On November 25, 2017, a 28-year-old woman from Newcastle-under-Lyme was arrested on suspicion of misconduct in a public office. She was subsequently released under investigation and as the investigation is ongoing, there is no further update at this time.
"On January 26, a 25-year-old woman from Newcastle-under-Lyme was arrested on suspicion of misconduct in a public office. She was subsequently released under investigation and, as the investigation is on-going, there is no update at this time.
"On January 30, a 21-year-old woman from Burton was arrested on suspicion of misconduct in a public office and conveying an article into a prison. She was subsequently released under investigation and as the investigation is on-going, there is no update at this time."
The investigations follow the prosecution of HMP Dovegate prison officer Adrian Kedzierski last month.
Stafford Crown Court heard the 50-year-old, of Craven Street, Burton, was paid £1,000-a-time for smuggling in Class B drug "mamba" and a mobile phone.
He was warned by the judge he could expect a "substantial" prison term and be sentenced at the same court on Tuesday, March 20.
