A methane leak that sparked an explosion at a coal mine in eastern Iran killed at least 31 people, the country's interior minister Eskandar Momeni said on Sunday.
Iranian state media had reported earlier in the day that 51 people had been killed in the explosion.
At least 16 others were injured by the explosion 8 in Tabas, about 540km south-east of Tehran, the minister said. About 70 workers were present at the site in South Khorasan province when the explosion occurred at about 9.00pm, it added.
According to the report, a leak of methane gas led to the blast in two blocks of the mine, which is owned by the private Iranian firm Madanjoo.
Authorities were sending emergency personnel to the area after the blast on Saturday. State TV broadcast footage of ambulances and helicopters arriving at Tabas to take the injured to hospital. Online footage from Irna showed the bodies of some of the victims being carried out of the site on mining carts.
Iran's President Masoud Pezeshkian, who was preparing to travel to New York for the UN General Assembly, announced that he had ordered all efforts be made to rescue those trapped and assist their families. He said an investigation into the incident had been launched.
“Unfortunately, we learned that an accident occurred in one of the coal mines in Tabas and a number of our compatriots lost their lives. I offer my condolences to their respected families,” Mr Pezeshkian said in remarks carried by state TV before departing for New York.
Vice President, Mohammad Reza Aref, spoke with cabinet members to ensure “emergency follow-up” and support for the victims and their families, Irna said.
Iran's Red Crescent said search and rescue operations were under way in the mine, where some workers remained trapped. Earlier, reports put the number of trapped workers at 24.
According to Irna, the workers were about 250 metres below the surface, cut off from rescuers by chambers that had filled up with concentrated methane gas.
“Gas accumulation in the mine” has made the search operations difficult, local prosecutor Ali Nesaei said. “Currently, the priority is to provide aid to the injured and pull people from under the rubble,” Mr Nesaei said, adding that “the negligence and fault of the relevant agents will be dealt with” later on.
Iran is rich in a variety of minerals. It consumes about 3.5 million tonnes of coal a year but produces only about half of this locally. The rest is imported, often for use in the country’s steel mills.
This is not the first disaster to strike Iran’s mining industry. In 2013, 11 workers were killed in two mining incidents. In 2009, 20 workers were killed in several incidents. In 2017, a coal mine explosion killed at least 42 people.
Lax safety standards and inadequate emergency services in mining areas are often blamed for the fatalities.