KARAGANDA, Kazakhstan -- Kazakhstan held nationwide mourning on Sunday after 42 people died in a blaze at an ArcelorMittal mine, the worst accident in the Central Asian country's post-Soviet history.

The tragedy, which struck at the Kostenko coal mine in the Karaganda region Saturday, came after a series of deadly incidents at ArcelorMittal mines and has prompted the nationalisation of the company's local affiliate.

"As of 3 pm (0900 GMT) the bodies of 42 people were found," Kazakhstan's emergency services said on social media.

"The search for four miners continues."

Rescuers earlier warned that finding the remaining miners alive were "very low", due to the lack of ventilation and the force of Saturday's explosion, which spread over two kilometres (1.2 miles).

The death toll overtook a 2006 accident that killed 41 miners at another ArcelorMittal site. It also came just two months after another incident killed five miners.

Anger and disbelief reigned after the disaster in Karaganda, central Kazakhstan.

"Every miner is a hero, because when he goes down, he does not know if he will come back or not," said former miner Sergei Glazkov.

Many welcomed the government's move towards nationalisation, angered by the company's safety record.

Daniar Mustafin, a 42-year-old salesman, said he favoured "full nationalisation without material compensation for the current owners".

President Kassym-Jomart Tokayev has ordered cooperation with the Luxembourg-based company to be "brought to an end."

- 'Worst' company in 'Kazakhstan's history' -

Speaking to victims' relatives at the mine, Tokayev called ArcelorMittal "the worst enterprise in Kazakhstan's history in terms of cooperation with the government".

The Kazakh government and the steel giant announced a preliminary agreement to "transfer ownership of the (local) firm in favour of the Republic of Kazakhstan", Prime Minister Alikhan Smailov stated.

"ArcelorMittal can confirm that the two parties have... signed a preliminary agreement for a transaction that will transfer ownership to the Republic of Kazakhstan," the global steel giant stated, adding it was committed to "finalising this transaction as soon as possible".

On Sunday, flags were at half-mast to mark the day of national mourning declared by Tokayev, an AFP correspondent saw.

Since the collapse of the Soviet Union in 1991, about 200 miners have died in Kazakhstan, the vast majority at ArcelorMittal sites.

- 'His guardian angel saved him' -

There were 252 people inside the mine when the fire started, ArcelorMittal said.

Outside a hospital in Karaganda, relatives of those who had survived the blast were thanking the heavens.

"His guardian angel saved him. He is alive," said Nikolai Bralin, the brother of an injured miner.

"Two of his ribs were slightly torn apart from the blow and he had surgery to put them back in place," he added.

Local politicians also called for the immediate nationalisation of the company.

"They must answer before court because they did not ensure people's safety," said local MP Kudaibergen Beksultanov.

"The state needs to take it upon itself now."

The group's arrival in Kazakhstan in 1995 was initially seen as a beacon of hope during the economic slump that followed the fall of communism.

But a lack of investment and inadequate safety standards were repeatedly criticised by the authorities, while trade unions called for tighter government control.

ArcelorMittal, led by Indian businessman Lakshmi Mittal, operates some 15 factories and mines in the centre of the former Soviet republic.