Police spokesperson Lieutenant Colonel Andre Traut said police were on the scene and monitoring about 1 000 locals.
"Police members will remain in the area to maintain law and order until we are satisfied that the situation has been contained," he said.
Protesters, attempting to prevent commuters from going to work, threw stones at trains, Traut said.
Earlier, they stoned vehicles on Jakes Gerwel Drive and Bluegum Road, said metro police deputy chief Yolande Faro.
"The situation inside Langa is still volatile. SAPS, metro police, traffic services and law enforcement are on the scene," she said.
News24