An enormous blast in the US that killed two people, obliterated two homes and made dozens more uninhabitable came with no hint of warning, and the home owner wondered whether a faulty furnace was to blame.

Fire officials expressed amazement that only two people died in the Indianapolis explosion, which rocked several houses from their foundations. Hundreds of residents evacuated. A fire burned for hours, engulfing dozens of homes.

The owner of the house that exploded, John Shirley, told The Associated Press that he received a text message last week from his daughter about a problem with the furnace at the house the girl shares with her mother and her mother's boyfriend.

He said that when he asked if the furnace had been fixed, his daughter said yes, and he wasn't aware of any additional problems until he heard from his daughter again after the blast.

"I get a text from my daughter saying 'Dad, our home is gone. Then I called my ex-wife and she said what happened," he said.

Shirley said no one was home at the time of the explosion. His ex-wife, Monserrate Shirley, declined to comment.

Investigators said they have not determined a cause for the blast. Public Safety Director Troy Riggs said the search for answers could take some time.

Crews have been inspecting gas mains in the neighbourhood but so far have detected no leaks, a spokesman said.

Deputy Code Enforcement Director Adam Collins said 80 homes were damaged, including 31 that might need to be demolished. He estimated the damage at US$3.6 million.

Mark Karnes, whose house is four doors down from the blast site, hoped to retrieve clothes and look for his cat. But he questioned the wisdom of going back inside the house.

"Because the walls bowed out and separated from the ceiling, I don't think it's safe," he said.

The blast flattened the house Shirley co-owns with his ex-wife and one next door that belongs to Jennifer Longworth and her husband, John.

The coroner's office had not yet identified the two people killed in the blast, but a candlelight vigil was held Sunday at the school where Jennifer Longworth teaches.

"They were just very sweet people," John Shirley said.

- AP