Iran's Interior Minister Eskandar Momeni on Sunday said an incident at a coal mine in eastern Iran killed at least 31 people and left 16 others injured. 

Momeni added that 17 miners were still missing. Their fate remained unknown as rescue teams were still 400 meters away from their presumed location.

The deaths were at a coal mine in Tabas in South Khorasan province, some 540 kilometers (335 miles) southeast of the capital, Tehran.

What do we know so far? 

The explosion occurred on Saturday at about 9 p.m. (1730 GMT/UTC). The accident was reportedly caused by a methane gas explosion in two blocks of the mine run by the Madanjoo company.

State media earlier said at least 51 people were killed and 20 others injured in an incident that left about 24 people trapped underground.

The total number of workers in both blocks when the blast happened was 69, state media said. Footage was broadcast in Iran of dead people in their work uniforms being pulled out of the mine.   

Iranian President Masoud Pezeshkian expressed his condolences to the victims in remarks that were broadcast on state television.

"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," Pezeshkian said. 

The Iranian president has ordered all measures to be taken to rescue the victims and also stated that an investigation has been opened into the disaster.  

According to local prosecutor Ali Nesaei, "gas accumulation in the mine" has complicated search and rescue efforts. 

"Currently, the priority is to provide aid to the injured and pull people from the rubble," Nesaei said, according to state outlet IRNA.    

How common are deadly mine disasters in Iran? 

While Iran is widely known as an oil-producing country, it is also rich in various minerals, including coal. About 1.8 million tons of coal is extracted from Iranian mines each year.  

Deadly disasters occur on a relatively regular basis in Iran's mining industry.

In 2009, 20 workers died in several incidents. Eleven workers were killed in two separate mining incidents in 2013. A coal mine explosion killed at least 42 people in 2017.

Loose safety standards and the lack of emergency response in mining areas are often blamed for the deaths.

wd, rc/rm (Reuters, AFP, AP)