CHICAGO (CBS) — Firefighters are responding to reports of a “major explosion and fire” Monday morning at the General Iron scrap yard in Lincoln Park.

Chicago Fire Department officials said they responded to a call of an explosion at the General Iron Industries scrap metal recycling plant at 1909 N. Kingsbury around 9:10 a.m.

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In a statement on Twitter, General Iron said no one was injured in the explosion, which happened “within our metal shredding process.”

“Shredding has ceased at this time. We are investigating all possibilities, including potential sabotage. We are fully cooperating with City officials,” the company said in a statement.

Ald. Brian Hopkins (2nd) tweeted there had been a “major explosion and fire” at the plant, and said witnesses reported seeing a “fireball and ‘mushroom cloud’ of smoke generated by the explosion.'”

Hopkins also claimed there was a “sudden increase in pollution readings” in the neighborhood after the explosion, but Fire Department officials later said air quality tests on-site revealed “no apparent immediate health risk to residents and the surrounding community.”

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The Chicago Department of Public Health planned to conduct further tests, and the Fire Department was investigating the cause of the explosion.

“Should any environmental violation be determined, the City will issue citations immediately. Work at the site has stopped as a result of the incident and will not resume until the City has determined the cause of the explosion. The health and safety of Chicago’s residents remain a top priority, and we will continue to provide more information as details are gathered,” Fire Department spokesman Larry Merritt stated in an email.

The U.S. Occupational Safety and Health Administration is investigating the incident. An OSHA spokesperson said General Iron has been cited once in the past five years, for three “other-than-serious” safety violations (the lowest category) in October 2016. The company paid a penalty of $5,704 for violations of machine safety procedures.

For the past few months, community activists have been urging aldermen and Mayor Lori Lightfoot to permanently close the facility, saying it creates dangerous pollution.

During a virtual City Council meeting last month, a doctor who lives near the scrap metal recycling plant said it creates a “cloud of pungent odor” in the area, and said it’s “absurd” the city is allowing the facility to continue emitting pollution during a respiratory pandemic.

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According to published reports, the Lightfoot administration ticketed the scrap yard five times in December and January for pollution issues. Each of the violations issued suggested pollution-control equipment required by the U.S. EPA failed to properly control harmful emissions from the facility.