Three people died when two trucks collided head-on on the N2 in Weza area, near Harding, on Thursday morning.
A case of culpable homicide was opened, and circumstances surrounding the incident were being investigated by the Harding police, Captain Nqobile Gwala said.
The accident occurred at about 05:15.
"The three people were declared dead at the scene," Gwala said.
KwaZulu-Natal Emergency Medical Services spokesperson Robert McKenzie said, apart from the three fatalities, one person was critically injured, and treated by their paramedics at the scene before being taken to hospital.
The crash resulted in a total road closure, causing traffic to be diverted via an alternate route, he said.