An explosion at a U.S. Steel plant in Clairton, Pennsylvania, near Pittsburgh, resulted in numerous injuries and left several individuals trapped under debris on Monday. Emergency responders are currently on the scene conducting rescue operations. The explosion occurred around 10:51 a.m., sending thick black smoke into the sky over the Monongahela Valley, a region known for its steel production for over a century.

Kasey Reigner, a spokesperson for Allegheny County Emergency Services, confirmed that one person has died, while two others are still unaccounted for. Multiple individuals have been treated for injuries, and the county dispatched 15 ambulances to assist with the situation. Local construction worker Zachary Buday described the explosion, stating, "It felt like thunder. Shook the scaffold, shook my chest, and shook the building, and then when we saw the dark smoke coming up from the steel mill, it’s like something bad happened."

The Clairton plant is the largest coking operation in North America and is one of four major U.S. Steel facilities in Pennsylvania, employing thousands of workers. Democratic Senator John Fetterman, a former mayor of nearby Braddock, expressed his condolences, calling the incident "absolutely tragic" and pledging support for the affected steelworkers. "I grieve for these families. I stand with the steelworkers," he said.

In response to the explosion, the Allegheny County Health Department is monitoring air quality and has advised residents within a mile of the plant to stay indoors, close windows and doors, and set air conditioning systems to recirculate. Officials reported that air quality monitors have not detected levels of soot or sulfur dioxide exceeding federal standards.

The Clairton plant has faced scrutiny over pollution issues in recent years. In 2019, the facility settled a lawsuit for $8.5 million, agreeing to invest $6.5 million to reduce soot emissions and odors. The plant has a history of environmental violations, including a significant fire in 2018 that caused $40 million in damages and led to the release of sulfur dioxide, prompting health warnings for local residents.

David Masur, executive director of PennEnvironment, called for a thorough investigation into the explosion's causes and questioned the plant's operational safety. "There needs to be a full, independent investigation into the causes of this latest catastrophe and a re-evaluation as to whether the Clairton plant is fit to keep operating," he stated.

Clairton Mayor Richard Lattanzi expressed his sorrow for the victims, noting the plant's significance to the community. "The mill is such a big part of Clairton. It’s just a sad day for Clairton," he said.

The incident has raised concerns about the safety protocols at the plant, which has been involved in multiple lawsuits regarding air pollution violations. U.S. Steel recently announced a partnership with Nippon Steel, which has been under scrutiny due to national security concerns and political implications surrounding the deal.