Milnerton police had to call for backup after a stray dog was found dragging the body of a newborn on a black bag because the dog would not let them near.
The station's spokesperson Captain Nopaya Madyibi said they are trying to track down the mother of the baby boy who was found dead on a black bag along Taurus Street in Phoenix, last week.
She said an anonymous resident had called the station, at just after 7.30am, to report seeing a dog dragging a black bag with a dead baby on it.
When police arrived, the dog was lying in front of the bag and growled and barked at them when they tried to approach.
"My colleagues then called for backup, so that the dog could be distracted," she said.
When more officers arrived, the dog was lured away and police could investigate, said Captain Madyibi.
The body still had an umbilical cord attached, so is suspected to have been stillborn, she said.
"No arrests have been made," she added.
She said the stray dog protected the dead baby, which is something she and her colleagues had never witnessed before.
Captain Madyibi has asked anyone that anyone who has seen or heard anything relevant to the case to call Crime Stop on 08600 10111.