San Jose residents were evacuated from their homes following an underground explosion Saturday. Authorities blocked off the area following the blast. Hazardous materials investigators are still monitoring the scene. Fire officials say the combustible gas that caused the explosion has dissipated. The gas resulted from some type of waste, possibly gasoline, being dumped into an underground sewer drain. Evacuated residents were taken to a nearby community center. There is no apparent above ground damage. No injuries were reported. Investigators are looking into what or who caused the explosion.