At least 35 of the miners who got trapped in a coalfield in Iran’s Golestan on Wednesday have died, state media reported on Thursday. They got trapped in Zemestanyurt mine after a suspected gas explosion. Several others sustained injuries after workers tried to jump-start a vehicle, Reuters reported.

Fears that poisonous gases were still present within the tunnels hindered rescue operations. “Unfortunately, all miners trapped in the wreckage lost their lives,” Minister of Cooperatives, Labor and Social Welfare Ali Rabiei told the press.

Officials were planning on digging a tunnel to gain access to the trapped miners, according to Al Jazeera. The country has suffered several major mining accidents in the past. In 2013, 11 workers died in two separate mining incidents, and number of mishaps claimed the lives of at least 20 miners in 2009.

Iran is highly dependent on its domestic coal supply as the bulk of it is used in steel production. In 2016, the country extracted 1.68 million tonnes of coal.