Fire investigators from the Valley Regional Fire Authority have determined that the cause of a fire that destroyed a single-wide mobile office structure early Monday morning in the Auburn Railroad Yard was incendiary in nature.

The investigation is ongoing. Damage is estimated at $75,000.

At 2:27 a.m., firefighters responded to multiple reports of a building on fire at the railroad yard in the 500 block of A Street Southeast.

When firefighters arrived, the mobile structure was completely engulfed in flames. Firefighters confirmed the structure was unoccupied and initiated a defensive attack, protecting an adjacent structure.

There were no injuries reported to firefighters or civilians.