A two-alarm fire in a Fenway apartment building that displaced 28 residents on New Year’s Eve likely started in the ceiling of a vacant third-floor apartment, a Boston fire official said Tuesday morning. The fire traveled along pipes inside the building, spreading to units on the fourth floor of the five-story building at 25 Peterborough St., said Steve MacDonald, the department spokesman. There were no rescues or injuries. Damage is estimated at $500,000, he said. Fire investigators have not yet determined the cause of the fire, which began at about 5:30 p.m. “It’s still under investigation, but they’re concentrating in the ceiling area of a third-floor apartment,” MacDonald said. “[Fire investigators] have to follow up with the management company to see if any work was being done in the apartment.” The 30-unit apartment building is owned by Reservoir Manor Corp. of Westwood, and is valued at $2.8 million, according to city assessing records. A message left with the company’s answering service was not returned on Tuesday. The fire displaced a total of 28 residents, six of whom were placed in hotel rooms by the Red Cross, MacDonald said. “The other 22 people were able to stay with family or friends,” he said.