A house fire in the 4000 block of Market St. in Piru started about 1:40 p.m. The structure was completely engulfed in flames when the Ventura County and Fillmore Fire Departments arrived. Exploding small arms ammunition slowed firefighting activity for a short time. Approximately seven retired L.A. firefighters, who were working on a nearby Habitat for Humanity project, were first to assist at the scene, see photo page 2. Complicating the situation was a live power line which fell across the access road. No injuries were reported. Neither the cause nor the damage estimate were available at press time.