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CHICAGO —A large fire in a South Side scrap yard Thursday morning triggered a hazmat response after a small explosion.

Firefighters responding to the call in the new city area just after 5 a.m. could see the flames from two blocks away.

The fire spanned a block from Morgan to Aberdeen north of 49th Street. The area contained abandoned trailers, pallets and other scrap.

The hazmat unit was called after firefighters heard what sounded like a gas can exploding, but there was little danger to residents.

Due to the early hour, the Chicago Fire Deputy Chief Carmelita Wiley-Earls believes the fire may have spread for some time before being discovered.

The cause of the fire is under investigation.