Emergency crews had worked through the night, digging through rock to try to reach survivors.

Video footage showed miners emerging blackened and bleary-eyed accompanied by rescuers at the facility in Amasra, on the Black Sea coast.

Family and friends of the missing could also be seen at the mine, anxiously awaiting news of their loved ones.

With the discovery of the latest bodies, the massive rescue operation is - in the words of the energy minister at the scene - approaching its end.

Interior Minister Mr Soylu told reporters: "We have counted 40 dead in total. Fifty-eight miners were able to be rescued, either by themselves or thanks to rescuers."

President Recep Tayyip Erdogan - who is on his way to Bartin province, where the mine is located - said on Twitter that the judicial authorities would investigate.

The local prosecutor's office has already begun an investigation in the blast, the cause of which is not known.

It is believed to have occurred at around 300m deep. At the time, some 49 people had been working in the "risky" zone between 300 and 350m underground, Mr Soylu said.

Energy Minister Fatih Donmez said there were initial indications the blast was caused by firedamp, which is methane forming an explosive mixture in coal mines.

There were partial collapses inside the mine, he said, adding that there were no ongoing fires, and that ventilation was working properly.

Amasra's mayor Recai Cakir said many of those who survived had suffered "serious injuries".

One worker who managed to escape on his own said: "There was dust and smoke and we don't know exactly what happened."

The mine belongs to the state-owned Turkish Hard Coal Enterprises.

Turkey witnessed its deadliest coal mining disaster in 2014, when 301 people died after a blast in the western town of Soma.