Story highlights "We are turning this into a criminal homicide investigation," official says

Investigators want information about a white van and its occupants

The couple killed in the explosion was buried Monday

Police want to know about a white van seen in the neighborhood before the November 10 blast that leveled several homes, Marion County Prosecutor Terry Curry said. Neither Curry nor other investigators released any more details on the matter, saying only that a "parallel investigation" had been going on while they were trying to figure out the cause of the explosion.

"At this point, we are here to inform you that we are turning this into a criminal homicide investigation," Gary Coons, the city's homeland security chief, told reporters. The officials took no questions after the Monday evening announcement but asked the public to come forward with any information about the van and its occupants.

The news came the same day that the couple killed in the blast, John Dion Longworth and Jennifer Longworth, were buried. Indianapolis Mayor Greg Ballard said he attended the funeral Mass, and "I could not even imagine what the families are going through."

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"But there is a secular side to this," Ballard said. "There is a search for truth, and there is a search for justice."

The late-night blast destroyed several homes and severely damaged more than 30, investigators said. At one point, 60 to 70 firefighters fought the resulting fires.

The local Crime Stoppers organization has offered a $1,000 reward for information leading to an arrest, and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives has offered $10,000 for information leading to an arrest and conviction, Curry said.