SEOUL, South Korea -- Six people died when the roof of a mine in North Korea collapsed in January, the North’s state media reported Monday, in a rare admission of a deadly accident in the secretive country.

Seven miners were initially trapped after the collapse Jan. 9 at the Unryul mine, a leading iron ore producer in the country’s southwest, North Korea’s main newspaper Rodong Sinmun reported. It said one was rescued 10 days later but six others were found dead.

The newspaper said the accident was the worst at the mine in South Hwanghae province since it was established.

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North Korea’s highly controlled state media rarely report news that might be considered negative, and an admission of fault by the government is unusual. Many North Korea watchers were surprised when the country’s state media reported in 2014 that government officials had offered an apology for the collapse of an apartment building under construction in Pyongyang, the capital.

The mine accident, which hadn’t been reported by outside monitoring groups before the North Korean media report, proved again how difficult it is to obtain information about the North. Rival South Korea has a mixed record on reporting developments across the border. Last year, it said a former North Korean military chief had been executed, but he was later found to be alive and holding several new senior-level posts.

The newspaper, run by the ruling Workers’ Party, said the January accident occurred when miners were launching “all-out” efforts to fulfill an order by leader Kim Jong Un to produce more ore for factories under a five-year economic development plan.

The sole survivor, identified as Kim Kyong Nam, said the victims could have made it out safely when they heard the sound of the collapse, but didn’t immediately leave because they first tried to check the situation in the mine, the newspaper said.

“The six miners left the echoes of their genuine, noble lives as the working-class” citizens, the newspaper said.

It said Kim Kyong Nam and two other miners trapped near him tried to survive by drinking water dripping from rocks and struggled with scant oxygen that made it difficult even to talk.

The newspaper said the accident occurred days before an anniversary of a visit to the mine years earlier by the father and grandfather of leader Kim Jong Un. It said the final words of the six dead miners to their families before the accident were about the Jan. 23 anniversary, such as their resolve to complete their monthly production plan before the date.

Kim Jong Un’s family is at the center of an intense cult of personality, and portraits of his father and grandfather are hung in public buildings and homes. Stories of North Koreans risking their lives to protect the portraits are a staple of state propaganda.