The explosion happened after heating gas leaked while the workers were carrying out repairs in a boiler room Iran is at a heightened risk of such incidents because of its aging infrastructure TEHRAN, Iran: Iranian state TV says a gas explosion in a Tehran sports complex has killed three workers. It says the explosion in the capital happened after heating gas leaked while the workers were carrying out repairs in a boiler room late Tuesday. Iran is at a heightened risk of such incidents because of its aging infrastructure, which it has struggled to maintain through years of Western sanctions. The country also has poor enforcement of safety measures. Last month, five workers were killed over leakage of toxic gas and fire in two separate incidents in Tehran.