On August 26, 2000, at 1800 hours Pacific daylight time, an experimental Fogerson RV-6A, N888LH, was substantially damaged when the aircraft lost engine power and struck a tree during an off-airport emergency landing while on landing approach to the El Monte, California airport. The private pilot and one passenger were not injured. The owner operated the amateur built aircraft under 14 CFR Part 91. Visual meteorological conditions prevailed for the flight and no flight plan was filed. The personal flight originated at Bakersfield, California, at 1645. The pilot reported that the flight was routine until on 2.5-mile final approach when he reduced engine power and raised the nose of the aircraft to slow to flap extension speed. He completed the landing checklist at the same time by setting the mixture control to the rich position, turning the fuel boost pump on and extending the flaps. When he restored engine power to stabilize the descent there was no response from the engine. He checked the mixture position, throttle position, fuel selector, and engaged the starter and lowered the nose of the aircraft; all to no avail. He identified an off-airport landing location, transmitted "mayday" to the tower, maintained flying airspeed, and landed. Postaccident examination did not reveal why the engine lost power.