The driver of the single decker bus is also still trapped, the City of Johannesburg said in an updated statement about the accident.
The ER24 spokesperson Russel Meiring said emergency service personnel are working to try and rescue the man.
The two metro buses collided while travelling at Jan Smuts drive this morning causing heavy traffic delays.
Johannesburg Metro Police Department (JMPD) and rescue workers are on the scene.
EMS Nana Radebe said patients that were taken to the hospital sustained both minor and serious injuries.
JMPD also confirmed that one driver had died in the collision.
WATCH: Passenger describes the Metro Bus crash
Meiring said there was a six months pregnant woman who was trapped. She had since been taken to a private hospital where she succumbed to her injuries, Radebe confirmed.
Jan Smuts Avenue has been closed to traffic due to the crash. Motorists are advised to use Oxford Road as an alternate route.
Speaking to The Citizen, Wayne Minnaar from JMPD said it was unclear what the main cause of the collision was, as investigations are still ongoing.
Three people – two women and a male driver – remain trapped in the buses in critical condition.