On September 17, 2020 at 11:09 am, the Farmers Branch Fire Department was dispatched for a structure fire at 11601 Lago Vista West #1156.   Quint 133 arrived on scene with nothing showing and began an investigation.  No audibles or strobes were activating.  A fire alarm technician approached the crew and advised the fire alarm system was being worked on, but a fire occurred in apartment #1156 with one sprinkler head activation.  Upon arrival to the apartment, the door was closed.  Resident was in the hallway.   Upon entering the apartment, light smoke was observed and one head had activated in a bedroom.  The fire had been extinguished.  Sprinkler system and fire pump were turned off.  Quint 133 requested an investigator.  Investigation determined the fire started along a base board by a dresser where a laundry basket of clothes were stacked.  The cause of the fire is undetermined at this time.  Estimated loss is $15,000.