The suspect was arrested on Monday after the children were sexually assaulted on a farm in Ceres at the weekend.
Western Cape police’s Andre Traut said the man was released on Tuesday night after being interrogated for 24 hours.
“We’ll continue our search for the suspect and we’re making an appeal to the public to assist us. They can call Crime Stop on 080 600 1011.”
Traut said authorities are still searching for at least one more man who they want to question in connection with the assault.
Sniffer dogs will also be taken to the farm where the incident occurred to search for clues.
Police have since released an identikit of the suspect.
Meanwhile, the mother of the seven-year-old boy told Eyewitness News she is heartbroken.
The woman, a distraught mother of five, sobbed bitterly saying she is not coping well.
She said her son has had nightmares following the incident and added that the boy hasn’t been speaking much.
The child has since left his mother’s home and is staying with relatives in a nearby farm at the moment.
Warning to rapists
Western Cape Police Commissioner Arno Lamoer on Tuesday issued a stern warning to rapists, saying the man responsible for this incident would be brought to book.
Lamoer said he’s confident there will be a breakthrough in this case as investigators are working tirelessly to track down the suspects.
He said some of his best officers are working on the case, including members of the visible policing and tracking units.
The police commissioner later added the incident left him sickened.