A naturally occurring methane gas leak prompted the evacuation of 16 homes here early Friday morning. Residents were being allowed to return to their homes later in the morning. A crew with Puget Sound Energy was doing routine checks Thursday night and discovered the methane gas, said a spokesman for the Valley Regional Fire Authority. PSE hired a private contractor that performed core samples. The gas was discovered on one side of the streets in the 31000 block of 133rd Avenue Southeast. And 911 was then called. The gas was found in some yards and in some cases in some houses. The levels were the highest in two homes, but even in those homes the levels were low.