The collision happened on Ottery Road near Schaapkraal on Saturday, and officials say the truck driver fled the scene.
Witnesses say the crash occurred just after 1pm when the heavy duty truck and a white Toyota Corolla collided.
The tiny baby was found lying outside the crumpled car, while the family, a mother, father and seven-year-old boy, and a fourth person, were trapped inside the vehicle.
Emergency workers had to cut the family out of the wreckage and they were all rushed to Groote Schuur Hospital.
ER24 spokesperson, Werner Vermaak, explains: “Four people sustained moderate to serious injuries and a seven-month-old baby died in a collision between a car and a truck on Ottery Road near Schaapkraal."
“Shortly before 2pm, paramedics from ER24, Metro EMS, Life Healthcare, Traffic as well as Fire and Rescue Services arrived on the scene."
“The seven-month-old baby was found outside the vehicle. It is believed that the child was ejected during the collision."
“Three occupants were trapped inside the vehicle. Fire and Rescue Services has to use hydraulic equipment to free them from the wreckage."
“Once freed, they were treated and rushed to Groote Schuur Hospital. The driver of the truck was not found on the scene,” Vermaak said.
Vermaak added the circumstances of the accident is still unknown at this stage.
Relatives of the injured family could not be reached on Sunday.
Police spokesperson, Captain FC van Wyk, says a case of culpable homicide has been opened for investigation.
He says members of Philippi police attended to the scene.
“On their arrival at the scene the members saw that a white Toyota Corolla collided with a truck. Four victims were inside the vehicle and two adults were seriously injured and a seven-year-old boy was slightly injured."
“A seven-month-old baby was declared dead on the scene. A culpable homicide case was registered for investigation,” Van Wyk said.
Anyone with info can call Philippi SAPS at 021 690 1500.