National SAPS spokeswoman Colonel Athlenda Mathe said: "It's unfortunate that one of the people arrested and in police custody is the mother of the baby herself. A more detailed press statement will be released."
A second senior officer with knowledge of the case confirmed that the mom's boyfriend has also been taken into custody. He was reportedly one of three people arrested when police swooped on a "suspicious vehicle" near the Mariannhill toll plaza on the N3 shortly after midnight on Sunday morning.
Acting national police commissioner Lieutenant General Khomotso Phahlane praised police for acting on the "apparent hijacking" when one-month-old Siwaphiwe Mbambo was taken near the City View shopping centre on Friday.
The white Toyota Yaris was found abandoned about 12km away in Moodie Crescent, Montclair, hours later.
Siwaphiwe, her car seat, pram and baby bag had all been removed.
"He would like to commend our police and all law enforcement agencies who have been on the ground since the news broke. We are happy that the baby found in a healthy condition‚" said Mathe.
