The victims include nine males and three females.
Ekurhuleni Emergency Management spokesperson William Nthladi said the bus crashed early Tuesday morning while traveling from Katlehong to Kempton Park.
Search and rescue operations are ongoing.
“The second phase of the rescue has not yet been conducted to confirm the total number of fatalities and injuries."
The bus driver has been hospitalized following the incident.
Meanwhile, on Monday, four learners were killed in an accident in Ekurhuleni.
The learners were from the Tom Newby and Rynfield Primary Schools, and a young learner was still at an early childhood development centre.
The MEC's spokesperson, Steve Mabona says a grade 3 learner was injured and rushed to a hospital.
On Sunday, nine people were killed when a bus rolled several metres down a steep embankment into thick bushes on the N2 after its tyre burst between Mandeni and KwaDukuza.
The bus had been transporting the Twelve Apostles Church parishioners in Trinity from Richards Bay to Shakaskraal.
Twenty five people have thus lost their lives over a three day period.
