A sprinkler system and a quick-acting shop steward helped prevent a fire reported at about 5:15 p.m. Tuesday from spreading beyond a student fabrication laboratory in the architecture building at the University of Arkansas, Fayetteville, university and fire officials said. No injuries were reported, said Willie Watts, a battalion chief with the Fayetteville Fire Department. He said department personnel arrived to find that something had been burning but never needed to deploy fire hoses. The room’s sprinkler system helped douse the blaze, he said, which was under control by 5:22 p.m.. Peter MacKeith, dean of UA’s Fay Jones School of Architecture, said at the scene that machines used by students were being shut down for the day when the problem started in a garden-level lab at Vol Walker Hall. A shop steward grabbed an extinguisher to try and put out the fire, MacKeith said, adding that he did not know what might have caused the blaze. The building was evacuated, but by 6 p.m. students were allowed to re-enter the building. MacKeith said he was unsure of any damage.