A blast in 2017 killed 43 miners in Azad Shahr city in northern Iran, triggering anger towards the authorities.
Mineral-rich Iran has around 1.5 billion tonnes of proven coal reserves, according to state media.
The Tabas mine covers an area of more than 30,000 square kilometres (nearly 11,600 square miles) and holds mass reserves of coking and thermal coal, according to IRNA.
It is “considered the richest and largest coal area in Iran,” IRNA said.