Gauteng Metrorail says it suspects that human error could possibly be behind the collision of two trains at the Eloff extension in Selby, south of Johannesburg, that left 112 people injured on Tuesday morning.This is according to Metrorail spokesperson Lillian Mofokeng who was at the scene following the accident that occurred just after 07:00. "We suspect and will look at the issues of human error so that we may see how it came about that two trains were allowed at the same section and at the same time," Mofokeng said. Metrorail train 9708 was travelling from Faraday towards New Canada when it collided head-on with Naledi-Jikeleza train 9949.Seven commuters sustained serious injuries while 105 others had minor injuries, she said. Metrorail was currently authorising trains manually because of a signalling upgrade underway within the area in which the incident had happened.Four crew members among those injuredShe added that the cause of the incident was still unknown but that technical teams were investigating. "We are hoping that we will assess the state of the infrastructure so that we can resume services as early as possible."Mofokeng added that four train crew members had also been taken to hospital for medical assessment. She said they would be receiving psychological support following the incident. Most of the passengers who were on the train did not have valid train tickets, Mofokeng added. "Currently we are utilising buses and only train commuters with valid train tickets will be allowed to ride on our buses," she said. Acting Transport Minister Thulas Nxesi has since directed the Railway Safety Regulator and the Passenger Rail Agency of South Africa (Prasa) to speed up the investigations into the cause of the collision. 'South Africans deserve safe public transport'"Following the outcome of this investigation, consequence management shall apply to all those who might be found to have negligently caused the crash," Nxesi said in a statement.Nxesi has also appealed to Prasa to accelerate the process of replacing all existing signalling interlocking systems and to ensure that standardised safety measures are always observed."We are doing so with the full appreciation that South Africans in the majority, the poor and the working class, deserve an efficient, responsive, safe and cost-effective public transport system," Nxesi added.Eyewitness Thembisa Lukwe who runs a creche near the railway track told News24 that she was shocked when she saw what had occurred. "I was walking out of the house when I heard a loud banging sound only to realise it was two trains that had collided," Lukwe said. She added that when she and other bystanders heard people crying, they ran to help passengers who were panicking.Scene cleared "When we saw what happened we ran to assist the passengers who were in the train. Others were injured while others were not. "We assisted them by showing them the way out so that they could access buses and also assisted paramedics to the entrance where they could get access to the injured passengers," Lukwe said. She added that there were a lot of schoolchildren on the train. She said they helped passengers who were in shock by offering them "sugar water". "It was chaotic and people were crying and panicking but I am happy that no one died," Lukwe added. The scene has since been cleared and the two trains were towed away by a diesel locomotive.