Seven people were killed and another 12 were injured on Saturday when a train travelling from Iran's second city of Mashhad in the northeast to Tehran derailed, an official told state-run television. "A train travelling from Mashhad to Tehran was derailed, resulting in the deaths of seven people and injuries to 12 others," Mohammad Reza Kazemi, the governor of Joghatai where the accident occurred, said. "The total number of passengers was 50, so there is a possibility that the number of casualties may rise." Kazemi said the derailment occurred near Mashhad in Khorasan Razavi province. "According to the train's engineer, the locomotive's brakes failed to work properly and we are investigating the matter," Kazemi said.