HARRISBURG, Pennsylvania: A fatal explosion at U.S. Steel's Clairton coke plant outside Pittsburgh has renewed debate over the future of the century-old facility, just as the company was working to stabilize its outlook through a major foreign acquisition.

The blast last week killed two workers and injured 10 others. Crews needed hours to locate two missing workers beneath the wreckage, and the cause remains under investigation. Clairton, the largest coke-making operation in North America, is central to U.S. Steel's Mon Valley operations, one of the few integrated steelmaking systems left in the country.

The disaster comes shortly after U.S. Steel secured approval for its nearly US$15 billion sale to Japan's Nippon Steel. President Donald Trump backed the deal in June, having already supported the industry with tariffs and a delay in stricter air pollution standards for coke plants. Nippon has pledged $11 billion in upgrades, with $2.2 billion targeted for Mon Valley facilities, and executives promised that steelmaking would remain rooted in the region.

"We wouldn't have done this deal with Nippon Steel if we weren't absolutely sure this facility was going to be around for a long time," U.S. Steel CEO David Burritt said. Nippon issued a statement reaffirming its "strong" commitment and said it had dispatched technical experts to assist local teams.

Yet the explosion could complicate those assurances. Two of Clairton's six oven batteries were destroyed, and two others are operating at reduced capacity. U.S. Steel has given no timeline for repairs. Union officials say persuading the company to reinvest in its facilities has long been difficult, and repair costs or new safety mandates could add financial strain.

Clairton has a troubled record. In February, another explosion injured two workers. In June, while Nippon was finalizing its acquisition, a breakdown released foul odors tied to hydrogen sulfide emissions. Environmental groups say U.S. Steel has paid $57 million in fines and settlements since 2020. A lawsuit over a 2018 fire concluded that the plant lacked effective maintenance and was "inherently dangerous" because of design flaws and neglect.

Matthew Mehalik of the Breathe Project argued the company has prioritized shareholder rewards, lobbying, and paying fines over safety.

For years, uncertainty hung over the Mon Valley, with workers doubting whether their jobs would last. Nippon's purchase was intended to resolve those doubts. Whether the Clairton disaster shifts that outlook is now unclear.