Redding Fire Department is investigating a fire that broke out in a field off Old Oregon Trail Thursday night. At around 6:15PM, Redding Engine #6 was heading back to the station from a medical call when they saw heavy smoke in a field near Tierra Oaks. They checked it out and found about an acre burning. Another engine was called and they were able to stop the spread. The fire is known to be human caused. Investigators will comb the scene for evidence Friday morning.