A pre-dawn fire burned a home where windows were covered with plywood storm shutters, turning the house into a "convection oven" and killing four children and an adult Thursday, officials said.

The fire did not reach the bedroom where the victims may have been sleeping, and they apparently died of smoke inhalation, Miami-Dade County (search) Fire Rescue Lt. Eugene Germain said.

Investigators were trying to determine what sparked the blaze, which began in the living room. The house became a "convection oven" when the boards and burglar bars trapped the fire's heat, gas and smoke, said Lt. Eric Baum, a fire-rescue spokesman.

The house did not have smoke alarms, and the victims may not have known there was a fire, Germain said.

Four of the victims died at the scene, and one died on the way to a hospital, he said. Their identities and relationships were not immediately known. A neighbor, Loretta Hanna, said the children were two girls and two boys, ranging in age from 11 to 16.

The children's mother was not home because she had recently given birth and was staying with a relative, said Arthur Brown, the children's uncle. The newborn was still in the hospital, officials said.

"I can't think. I've been crying all this morning," he said. "It hurts me because of those sweet little children."

Some homeowners in this city 25 miles south of Miami have left up storm shutters because of the three hurricanes that have hit Florida this year. "It poses a tremendous risk to the occupants to not have a reliable means to get out of the house," Baum said.

Neighbor Miriam Bonilla stared at the boards and burglar bars covering her own windows, 100 feet away from the scorched home. "We're going to take them off, for the Lord's sake," she said.