Two prison officers have been arrested after small quantities of cannabis and cocaine were recovered during house searches close to the Portlaoise and Midlands prisons.
Gardaí and detectives from the National Bureau of Criminal Investigation raided nine properties, including the homes of prison officers and suspected drug dealers, as part of an operation targeting the supply of contraband to inmates.
Officers also searched both prisons.
The men, aged 34 and 37 years old, are being held at Newbridge Garda Station.
Last May a major search of Portlaoise maximum-security prison yielded 17 smuggled mobile phones, five SIM cards and 11 phone chargers. Drugs, syringes and a budgie were also found.
Former minister for justice Michael McDowell ordered the search after an inmate phoned a radio talk show on a smuggled mobile phone.
Both officers are stationed at Portlaoise Prison and are thought to have around 15 years of service each. It is understood they were arrested at their homes.
Stephen Delaney, assistant general secretary with the Prison Officers' Association (POA), said the early-morning raid came as a surprise to jail authorities.
"I want to make it quite clear, as we have done in the past, that we will not and do not condone the smuggling of contraband into the Prison Service," Mr Delaney said.
"It only serves to undermine the work and safety of other staff.
"We will be co-operating with the garda investigation."
He said the POA had not been in contact with the men since their arrest.