Justice Minister Michael Masutha says he is seeking advice over the legality of a parole board decision to free the Olympic athlete on Friday.
Pistorius has spent 10 months in jail for shooting dead his girlfriend Reeva Steenkamp, after his conviction for manslaughter last year. The Olympic athlete insists he mistook Ms Steenkamp for an intruder.
Pistorius was jailed for five years for the culpable homicide of Reeva Steenkamp, a charge equivalent to manslaughter. Under South African law, Pistorius is eligible for release under “correctional supervision”, having served a sixth of his sentence.
The justice minister’s comments follow a petition from the Progressive Women’s Movement of South Africa, who have described the athlete’s early release as “outrageous” and “an insult” to victims of abuse.
“I’m confident that by Friday I would be in a position to determine whether legally I have the authority to do anything,” Mr Masutha is quoted by AFP news agency as saying.
Ms Steenkamp’s parents have said that the time Pistorius has served is “not enough for taking a life”.
This week, prosecutors in South Africa filed papers calling for the athlete’s conviction to be reviewed and converted to murder, which carries a minimum sentence of 15 years. His defence team now has a month to file its response.
After his release from prison, Pistorius would serve the rest of his term under house arrest.
During sentencing, Judge Thokozile Masipa said the state had failed to prove Pistorius’ intent to kill when he fired.
The double amputee shot and killed Ms Steenkamp through a locked bathroom door at his Pretoria home, believing she was an intruder, he told his trial.
Pistorius was born without the fibulas in both of his legs, and had surgery to amputate both below the knee while still a baby.
He went on to become one of South Africa’s best-known sports stars, and was the first amputee to compete against able-bodied athletes, at the 2012 London Olympics.