At least 30 miners were injured in an explosion at a coal mine in northeastern Iran and up to 80 others remained trapped underground, officials said.

Director of Iran's emergency services Pir Hosein Kolivand told the country's official television broadcaster on Wednesday that 36 miners had been treated for asphyxiation symptoms and that one of them was in a critical condition, local news reported.

Kolivand said the explosion at the mine, which is near Azadshahr in Golestan province, had affected two sections of the mine, leaving about 40 miners trapped in one part while between 30-40 others were trapped in a different shaft.

Some Iranian media reported there were at least two fatalities, but this was not confirmed officially.

According to the first reports, there was a gas leak before the explosion and rescue teams from various medical centers and the Iranian Red Crescent then attended the scene of the accident.

Rescue efforts have been hampered by amounts of methane gas accumulated inside the mine, where a secondary tunnel was being excavated to facilitate access to the trapped miners, the official said.