FORT WORTH (CBSDFW.COM) - A duplex caught fire around 4:15 p.m. Saturday due to a mechanical failure of the air conditioner which caused the unit to catch on fire, according to the Fort Worth Fire Department.

It happened at 9304 Mountain Lake Court which is a duplex.

The fire then crawled up the wall of the house and into the attic of the duplex which shares a common attic.

The duplex suffered the most damage.

The house next door also had some minor damage, due to the close proximity of the structures.

One firefighter suffered a minor injury when he fell down a stairwell.  He was treated at the scene.

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