The cause of a fire that took the life of Sunnyside businesswoman Tami Mathison, 50, last Thursday night is still under investigation, according to the Yakima County Fire Marshal's office. The fire at 1201 Northwest Crescent Ave., which broke out just after 11 p.m. Thursday night, claimed the life of Mrs. Mathison, whose body was recovered from the debris last Friday afternoon. Her body was turned over to the Yakima County Coroner's office for identification and cause of death. She was the only person unaccounted for in the fire. Her husband, Marty Mathison, and the couple's five children were able to escape. A family pet was also lost in the fire. According to Yakima County Fire Marshal Ron Rutherford, emergency workers had been unable to remove her body during the fire because of the intense heat from the structure's blaze. Firemen were further hampered when the second story collapsed into the first floor. The house also had a full basement, Rutherford said. Witnesses said Mrs. Mathison had been seen in one of the upstairs bedroom windows prior to her disappearance. Rutherford said she may have been confused by the smoke in her attempt to escape the fire. Heavy equipment was called in mid-morning last Friday to begin the clean-up. The fire caused in excess of $200,000 damage to the house and a car and van.