Late Tuesday afternoon, smoke was still wafting from the top of the charred buildings of the former Thunderbird Hotel at Jantzen Beach. Crews were still dousing a few remaining hot spots with water. The Portland Fire Bureau's John Harding says it's hard to know how long the fire was burning before crews arrived early Sunday morning. About 30 federal investigators from around the country are now on scene. They expect to finish safety review of the structure by mid-morning Wednesday. They will then start collecting physical evidence to determine the cause. Firefighters first arrived at the scene just before 3 a.m. Sunday. They called a fifth alarm at 4:23 and had the fire under control just after 7 a.m.