BAKERSFIELD, Calif. (KGET) -- Union Avenue was closed in both directions after a two-alarm structure fire broke out at an abandoned building on Union Ave. early Tuesday morning. According Alexander Clark, Battalion Chief of the Bakersfield Fire Department, crews received a call of a fully engulfed structure just before 6 a.m. on the west side of Union Ave. and 1st St. As BFD Engine 6 pulled up to the scene, firefighters reported a few homeless people gathering their belongings outside the structure as heavy fire shot out of the building. In the last two days a BFD fire crew also reported to the same location for reports of a small fire on the wood floor inside the vacant building, the Battalion Chief said. However, it is unknown if that was the case in today's fire, Clark added. The two-alarm fire prompted BFD and Kern County Fire Department to work together to contain the flames. Fire crews used up three ladder trucks, four fire engines and 36 personnel were involved in fighting the early morning inferno. Miraculously the flames managed to stay within the building as the vacant building's roof caved in and eventually burned out. Once the fire was extinguished, firefighters searched the inside of the building while arson investigators began to search for the cause of the fire. No injuries have been reported.