A rush-hour train crash in the township of Soweto in Johannesburg, South Africa, Thursday injured more than 850 people, three critically.

The train, which had been traveling between the Mzimhlophe and Phomolong stations in Soweto, slammed into a stationary train. Authorities are investigating whether the accident was due to human error or mechanical issues, said Metrorail Chief Executive Officer Mosenngwa Mofi, United Press International reports.

Most of the injured were treated on the scene, but 25 are still in the hospital, according to authorities, the BBC reports.

"This is the biggest incident in recent years, even though no one has died. People sustained serious multiple injuries," said Synock Matobako, spokesman for emergency services, the news agency reports.

Each day, more than 2 million mostly poor commuters travel on the nation’s aging trains, considered the continent’s most developed.

But the system is, unfortunately, no stranger to accidents.

Last month, a collision between two passenger trains north of Pretoria killed the driver and injured about 200 people. And last year, the luxury Rovos Rail train derailed, also near Pretoria, leaving three people dead. One of the nation’s deadliest crashes occurred in 1965, when 150 died after a commuter train derailed in the province of KwaZulu Natal.

(Photo: Reuters /STR/LANDOV)