Convicted NCA bomber Domenic Perre is recovering in the Royal Adelaide Hospital after undergoing heart surgery.
Perre collapsed in court last week soon after being found guilty of the murder of Detective Sergeant Geoffrey Bowen and the attempted murder of lawyer Peter Wallis.
He was taken to hospital last Thursday for what the Department for Correctional Services called a "medical episode".
During his trial, the court was told Perre had been unwell.
Sources have told the ABC that the 65-year-old was recovering in hospital after surgery to remove a blockage in an artery.
It is understood that Perre will be returned to the Adelaide Remand Centre within days.
In March 1994, Perre sent a parcel bomb to Detective Sergeant Bowen's Waymouth Street office, in revenge over the police officer's investigation into the Perre family's drug business.
Detective Sergeant Bowen was killed in the bombing and Mr Wallis received burns to 35 per cent of his body and lost an eye.
Perre was immediately identified as a suspect, but the first set of charges were dropped in September 1994.
He was charged again in 2018.
After a seven-month trial, Justice Kevin Nicholson found Perre guilty of murder and attempted murder.
Perre has been in custody since 2017 over unrelated drug and firearm charges.
He is expected to be sentenced for the murder and attempted murder in September.