UNIVERSITY PARK (CBSDFW.COM) – A two-alarm fire caused “substantial damage” to a two-story duplex Monday after it spread to the attic before fire officials arrived.

University Park Fire Department Chief Randy Howell said two families who lived in the duplex in the 4400 block of Glenwick were displaced. The emergency call came in at 11:38 a.m. Monday, he added.

None of the residents were home when the fire began. Howell said the building’s owner lived on the first floor and rented the second floor out.

Howell said the person who rented the room called police after she returned and found heavy smoke inside the building.

The chief did not know how the fire started nor a dollar amount of the damages.