PORT ORCHARD, Wash. (AP) — Authorities say four family members killed in a Port Orchard house fire over the weekend died from smoke inhalation.

The Kitsap County Sheriff's office on Monday identified the victims as 38-year-old Merle Simpson, his children 2-year-old Madison and 1-year-old Collin, and his 63-year-old mother Vili Simpson. Merle Simpson's father, Donald Simpson, escaped the house early Saturday.

The Kitsap County Fire Marshal is investigating the cause.

Donald Simpson told KING-TV his grandchildren were staying with him for the weekend. He recalled yelling to his wife that the house was on fire and telling her to get out. He says he went downstairs amid heavy smoke and thought she was behind him. He also saw his son at the top of the stairs and told him to come.

Simpson says he left the house hoping to catch his two grandchildren escaping the fire, but they never came out.