US authorities have launched a homicide investigation into a house explosion that killed a young couple and left numerous homes uninhabitable in an Indianapolis neighbourhood.
Indianapolis Homeland Security Director Gary Coons made the announcement after meeting with residents of the subdivision where the blast happened on November 10.
Funerals were also held for the two victims, who lived next door to the house where investigators believe the explosion originated.
"We are turning this into a criminal homicide investigation," Coons said, marking the first time investigators have called the case criminal.
Search warrants were being executed and officials were looking for a white van that was seen in the subdivision on the day of the blast, Marion County Prosecutor Terry Curry said. A reward of at least US$10,000 ws being offered.
Curry said the investigation was aimed at "determining if there are individuals who may be responsible for this explosion and fire."
Neither he nor Coons took questions or indicated if they had any suspects. No arrests have been made.
Officials have said they believe natural gas was involved in the explosion, which destroyed five homes and left dozens damaged, some heavily. Damage has been estimated at US$4.4 million.
Investigators have been focusing on appliances as they search for a cause of the explosion.
Hundreds of people attended the funerals for the couple killed in the explosion, 34-year-old John Dion Longworth and 36-year-old Jennifer Longworth.
She was a teacher remembered for knitting gifts for her students, while her husband, an electronics expert, was known as a gardener and nature lover.
Indianapolis Mayor Greg Ballard spoke at the news conference and said he went to the Longworths' funeral and had a hard time coming to peace with what had happened.
"There is a search for truth and there is a search for justice," Ballard said.
The couple lived next door to the house where investigators are focusing.
The co-owner of that house, John Shirley, said he had received a text message from his daughter recently saying the furnace in the home, which she shares with her mother and her mother's boyfriend, had gone out.
Shirley's ex-wife, Monserrate Shirley, said her boyfriend, Mark Leonard, had replaced the thermostat recently and the furnace had resumed working.
The couple was away at a casino at the time of the blast. The daughter was staying with a friend, and the family's cat was being boarded.