LYNN-Firefighters battled two house fires in Lynn since Monday that displaced families just before Christmas day.The first blaze occurred at 101 Grant St. at about 11:30 p.m. Sunday. According to District Fire Chief Rick Gecoy, one firefighter was hospitalized with minor injuries after responding to the fire.The roof of the home reportedly caved in during the fire.The second house fire happened at about 6:15 p.m. Monday at 18 Elvir St. When crews arrived, there was already a heavy fire condition on the second floor, Gecoy said.Firefighters had to force entry to the structure and cut through the roof, Gecoy added. No injuries were reported.Both fires are still under investigation.