(CNN)A gas explosion left 35 coal miners dead Wednesday in northeastern Iran, according to the state-run Islamic Republic News Agency.
Dozens killed in Iran coal mine explosion
At least 72 people were injured, 21 of them have left the hospital, according to IRNA.
Officials told IRNA that 22 bodies have been recovered.
It's believed at least 500 miners were working in the the Zemestan Yurt Coal Mine at the time of the blast, the news agency said.
Earlier Wednesday, officials blamed accumulated methane gas for the blast in the province of Golestan.
Dozens of miners were trapped in one section of the mine, while dozens more were trapped in another section, said Pir-Hossein Kolivand, head of Iran's Emergency Center.
The explosion took place at 12:45 p.m. local time Wednesday, according to IRNA.
Ambulances and rescue teams were dispatched to the scene near the city of Azadshahr.
Twenty-five people who entered the mine to help the trapped miners were taken to the hospital due to gas inhalation, said Hamidreza Montazeri, deputy head of the emergency department in Golestan province, according to Press TV.