India, Aug. 11 -- A massive explosion at the Clairton Coke Works steel plant in Pennsylvania on Monday morning left multiple people injured, officials reported. Emergency crews quickly responded as thick smoke billowed from the site. The full extent of the injuries remains unclear, according to Pittsburgh's Action News 4, as reported by The Daily Mail.

According to WTAE, a video from Sky4, Pittsburgh's sole news helicopter, captures the fire crew battling the flames after the explosion. Dispatchers have confirmed to the media outlet that multiple people have been injured; however, the extent of their injuries is unknown.

The cause of the explosion is unknown as of 11:30 am EST. Officials declared the explosion a mass casualty incident t...