A drone was used to drop contraband within the secure perimeter of Canberra's prison, and a detainee was caught on CCTV leaving after the jail's evening curfew to collect the goods.
The incident occurred in early June but ACT Corrections would not confirm the date, nor any specific details, only that the incident remains under "active investigation".
In a statement, Corrections said that "it would not be appropriate to provide specific details at this time".
They would however, confirm that prison staff received "intelligence" on June 21 "regarding the introduction of contraband by a drone in early June".
The matter has not been referred to police "at this stage", the statement said.
"The introduction of contraband into the AMC, whether by drone or other means, is an offence under the Corrections Management Act," the statement said.
Corrections would not disclose how the detainee managed to leave the secure building after curfew, whether the breach triggered an alarm, if contraband was recovered, or whether the CCTV footage of the incident identified the person involved.
"[Corrections] is taking all necessary actions in response to the identified security risks to prevent future occurrences and to investigate this incident," a statement from the Justice and Community Safety directorate, which oversees the prison, said.
"As these actions are still underway specific details cannot be provided at this time."
The incident comes after a series of revelations into how contraband is smuggled into the prison in the past 12 months.
A major security breach occurred in November last year, when a large package of contraband was thrown over the perimeter fence and landed in the secure area between the fence lines.
This triggered an alarm which was not investigated.
The offender who threw the contraband in then returned around four hours later , cut a hole in the fence with boltcutters, retrieved the package, and then threw it further into the prison yard beyond the secondary fence "into an area accessible by the detainees".
Prison guards did not find the hole in the fence until some 24 hours after the incident and an immediate lockdown and search of the cells and secure areas was conducted.
Undisclosed contraband such as mobile phones, hand tools, a hacksaw blade, drugs and drug paraphernalia was found during the search.
An internal management review of that incident was conducted, but the results of that review have not been made public.
Canberra's top secret prisoner, Witness J, a former intelligence officer who spent 15 months behind bars under a pseudonym for breaching Australia's national security laws in 2018 and has since written a book about his experiences called Here, There Are Dragons, said that contraband usually came into the jail from visitors.
However, visitors have been banned from entering the jail since March due to the risk of COVID-19 infecting the prison population. Crowded cell conditions within the prison make social distancing impossible.
Drones have been used to drop contraband into prisons throughout Australia but this Canberra incident marks the most recent and apparently successful attempt.
On Christmas Day last year, a drone dropped two packages into the prison yard at the Capricornia Correctional Centre in central Queensland, sending the jail into immediate lockdown.
In 2018, NSW Corrections Minister David Elliott confirmed there had been more than 60 instances of drones being flown above or near NSW prisons to potentially transport drugs inside the wire.