A tunnel collapse killed four workers building a new station for Tehran’s metro network, news outlets reported on Thursday. The fatal accident happened when a concrete cladding on a tunnel fell on the construction crew on Wednesday evening in the southern Kianshahr district, the news website Fararu reported. Sixteen workers, including some Afghan refugees, survived the cave-in and six injured who were taken to hospital for treatment. Rescuers were still searching for one worker Friday morning.”The accident was the result of human error,” said Tehran deputy mayor for traffic and transport, Maziar Hosseini. He did not elaborate. The municipality said it had set up a special committed to investigate. Tehran’s underground metro covers 180km and there are plans to add two more lines by 2018. The line where the accident happened is not in use yet. The subway system in the sprawling capital is used by nearly four million people every day.
