Investigators say two teenagers are responsible for setting a fire last week at an empty apartment building in Madison. Sergeant Ken Grimes with the State Fire Marshal’s office says the suspects are a 16-year-old boy and a 15-year-old girl. He says the boy also admitted to police his involvement.Firefighters were called to the building on Weston Avenue just before 3 a.m. Tuesday. It took them more than seven hours to put out the flames. Grimes says the teenagers were turned over to the custody of their guardians. The district attorney’s office and officials with the juvenile corrections system will determine if charges will be formally filed.