( CNN ) -- Four family members ' bodies were found after an intentionally set fire damaged a Florida home belonging to former tennis player James Blake , who was leasing it out , authorities said Wednesday . `` We have also confirmed that the fire was started intentionally by an unknown accelerant , '' Hillsborough County Sheriff Col. Donna Lusczynski told reporters . Two bodies had upper body trauma , Lusczynski said . The four apparent family members -- two adults and two teenagers -- were found in their respective bedrooms after the early morning fire , Lusczynski said . Identifying the bodies will take several days , she said . The adults were in one bedroom , and each teen was in a separate bedroom , Lusczynski said . Authorities found small commercial-type fireworks in the Tampa home , officials said . Blake was not at the home at the time of the fire , Lusczynski said . He was leasing the property and was contacted by phone after the incident by sheriff 's officials . Blake , 34 , was once ranked No . 4 in tennis among world singles and played in the 2006 Tennis Masters Cup , according to his Facebook page . At 5:45 a.m. Wednesday , authorities received a 911 call about an explosion and then a fire at the home . Firefighters began extinguishing the fire and then discovered two bodies inside the 6,000-square-foot house , authorities said . Crews found a third body and then a fourth , the sheriff 's office said . `` Due to the magnitude of the structural damage caused by the fire , this investigation will be a slow , meticulous process , '' the sheriff 's office said . CNN 's Marlena Baldacci contributed to this report .
NEW : Fire was `` started intentionally by an unknown accelerant , '' official says . NEW : Two victims had upper body trauma . NEW : Two adults are found in one bedroom , and teenage children in their own bedrooms . Former tennis pro James Blake , 34 , owns the house but was leasing it .