An early morning fire on Monday was the second blaze to strike a vacant duplex in Millville in less than two weeks. Authorities are investigating a fire at 312 E. Vine Street that broke out at about 4 a.m. Monday. The fire started in the rear of the house and took over two hours to bring under control. Another early morning fire damaged a duplex on Oak Street on August 28th and has been ruled “incendiary” in the preliminary investigation. No injuries were reported in either fire.