No one was hurt and no significant damage occurred when a fire broke out in a mixing vat at a Livingston Street mill building, Chief William Kenyon said. The fire at 35 Livingston St. was confined to the mixing vat in a room where soap products were made, Kenyon said, and appeared to have been started by an inadvertent mix of substances. The building sprinkler system came on immediately, he said, and kept the fire under control. Firefighters arrived shortly after that, since the department’s Branch Avenue station near the North Burial Ground was around the block and down the street from the building. Firefighters ran two hoses into the building to make sure the fire was doused, he said. No more information was immediately available.