Authorities are investigating the cause of a fire in Monessen late Thursday night. Firefighters from several departments were called out around ten-thirty to reports of a fire at a three-story wooden-frame house on McKee Avenue. Emergency dispatchers said that when crews arrived on the scene, flames could be seen going through the roof. The flames became so intense that at one point, firefighters were ordered out of the structure and told to fight the blaze from the exterior. Authorities say everyone inside was able to make it out safely.