A methane leak sparked an explosion at a coal mine in eastern Iran on Saturday, killing at least 30 people and injuring dozens, Iranian state television reported Sunday, with some 20 people still stuck in the mine.

The report said the deaths happened at a coal mine in Tabas, some 540 kilometers (335 miles) southeast of the capital, Tehran.

Authorities were sending emergency personnel to the area after the blast late Saturday, it said. Around 70 people had been working there at the time of the blast.

Oil-producing Iran is also rich in a variety of minerals. Iran annually consumes some 3.5 million tons of coal but only extracts about 1.8 million tons from its mines per year. The rest is imported, often consumed 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 separate 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.