A five-alarm fire destroyed three residential buildings and five vehicles in Lawrence on Saturday afternoon, the state fire marshal’s office said. The Hancock Street fire displaced residents in the buildings, said Jennifer Mieth, a spokeswoman for the state fire marshal, but there were no injuries. Kat Powers, a spokeswoman for the American Red Cross, said the structures included two single-family homes and a building of five apartments, four of which were empty. Powers said three families were displaced, including seven adults and two children. The Red Cross provided emergency funds for food and clothing to five residents, she said, and stuffed animals for the children. The Red Cross provided hotel rooms for two families, while the third chose to stay with relatives, she said. “We are grateful that nobody was hurt,’’ Powers said. “We were very happy to show up in Lawrence, but we always need more volunteers.’’ Mieth said the state fire marshal’s office was investigating the cause of the fire in cooperation with local authorities.