Iranian state media report that at least 35 workers have been killed in an underground coal mine explosion in northern Iran.
Officials told the state-run IRNA news agency that an accumulation of methane gas leaking into the mine caused the explosion on May 3.
Because the explosion was at a great depth, media reported that only 21 bodies had been recovered by late on May 3, though the explosion occurred nearly 12 hours earlier.
As many as 80 miners were underground when the explosion occurred at the Zemestanyurt coal mine in Iran's Golestan Province.
It was not immediately clear if only miners were killed or if some rescue workers were also among the dead.
Meanwhile, authorities have confirmed that at least 69 people were injured in the tragedy and in efforts to rescue the miners.
Authorities were continuing a rescue operation at the mine early on May 4 in an attempt to try to reach any survivors.
Some workers are believed to be trapped at a depth of 1,800 meters. The search teams by early May 4 had only reached a depth of about 800 meters.
Rescue teams were working against the clock, as it was not clear how long the air supply would last where the workers were trapped.