A six-month-old baby was kidnapped and his nanny almost killed in Bezuidenhout Valley, Johannesburg police said on Wednesday.
Lt-Col Lungelo Dlamini said police were searching for a Pakistani couple who were renting a room in the house where the attack took place on Tuesday.
"It is alleged that the couple were tenants at a house in Bezuidenhout Valley and had not paid rent for December 2012."
He said it was suspected they tried to kill the nanny by slitting her throat with a sharp object and taking the baby.
The nanny was found by the owner of the house in a critical condition before being taken to a local hospital.
"It is suspected that the couple with their three children are still in Gauteng. The woman is allegedly pregnant," Dlamini said.
Police appealed to anyone with information of their whereabouts to come forward.