The occupants told investigators they had detected an odor of propane a day earlier, but it was unclear what action was taken, if any, Niagara County Undersheriff Michael Filicetti said. The cause of the explosion was being investigated.
The force of the 6 a.m. explosion in the town of Wilson, about 30 miles north of Buffalo, reduced the large home to a pile of waist-high rubble that caught fire. It blew in a basement window and knocked pictures from the wall of the nearest neighboring home, about 100 yards away.
The sheriff's office said homeowners Jody and Judith Johnson, their 16-year-old son, Nathan, and 18-year-old daughter, Katie, were apparently thrown forward toward the road and survived. Sarah Johnson's body was found about four hours later in the charred debris at the rear of the home.
The parents and Nathan were hospitalized in stable condition later Tuesday. Katie Johnson was in critical condition with severe burns, authorities said.
"I heard a blast like nothing I've ever heard before in my life," said next-door neighbor Matthew Henderson, who at first thought his own house may have been struck by lightning. He said he rushed to a rear window and saw tufts of yellow insulation and papers blowing around the lawn.
"I knew it wasn't coming from here," he said. "Then I looked out (a side) window and saw the lack of the neighbor's house altogether."
Henderson said he rushed next door and found the injured victims distraught and disoriented amid broken glass, window frames and other debris.
"The father was on his elbows and knees and had his head buried in his hands on the driveway," he said. "They were calling for Sarah."
"I can't imagine they were able to comprehend what was going on," Henderson said. "I was disoriented myself."
Two other children, ages 10 and 16, weren't home at the time of the blast, which Filicetti said could be felt at the sheriff's communications center about 4 miles away.
The explosion occurred on a sparsely developed stretch of rural road, where a garage and barn remained standing on the property Tuesday. A basketball backboard and hoop mounted on a black pole stood out against the pile of smoldering rubble.
Neighbor Nate Reynolds said he was sleeping when a loud noise woke him up. At first he thought it was thunder, but soon began getting text messages from friends saying there had been an explosion.
"It sounded like a sonic boom," said Reynolds, who lives about a mile from the scene. "It shook my whole house."
Other neighbors said they heard and felt the blast, then saw a ball of flame rise over the house. Scores of firefighters from several local volunteer companies put out the blaze.
"It just seems like a nightmare. I'm in shock," neighbor Pam Henderson said. "My heart goes out to the family."