Kazakhstan held nationwide mourning on Sunday after 45 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 nationalization 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."

Later, authorities said the bodies of three others had been found and rescuers were searching for the last miner missing, with little hope of finding him alive. 

Rescuers earlier warned that chances of 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 kilometers (1.2 miles).

The previous deadliest mine accident in post-Soviet Kazakhstan occurred in 2006, killing 41 miners at another ArcelorMittal site. It 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 nationalization, angered by the company's safety record. 

Daniar Mustafin, a 42-year-old salesman, said he favored "full nationalization 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."

In a statement on its Kazakh website, ArcelorMittal said its thoughts were with the families of those who lost loved ones.

"We understand that there is no adequate compensation for their losses, but we will do everything in our power to support them in the coming weeks and months", it said.

"ArcelorMittal has owned these mines in Kazakhstan since 1995. Unfortunately, their operation poses a high safety risk due to the complicated geology, which has resulted in several deadly accidents over the past two years", it said.

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 favor of the Republic of Kazakhstan", Prime Minister Alikhan Smailov stated.

In its statement, ArcelorMittal said that the previous week, "the two parties… signed a preliminary agreement" to transfer ownership of the mine to Kazakhstan.

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. 

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

However, a lack of investment and inadequate safety standards were repeatedly criticized 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 center of the former Soviet republic.