Investigators are searching for clues in an Indianapolis neighbourhood devastated by a massive explosion and raging inferno that left two people dead and damaged more than 30 homes.

Fire officials say they do not know yet what caused the deadly blast at around 11pm on Saturday.

Speculation locally that a gas leak was to blame has not been confirmed.

Citizens Energy says its crews have not found any signs of an escape.

Officials have not released the identities of the two people who were killed.

However, a candlelight vigil was held on Sunday night at Southwest Elementary School in nearby Greenwood for teacher Jennifer Longworth and her husband, John Dion Longworth, who lived in one of the homes destroyed in the blast.

Around 200 people were forced to leave their homes following the explosion, with many of the 30 or so damaged houses now beyond repair.

The blast was so loud it woke people as far as three miles away, leading some to think a plane had crashed or there had been an earthquake.

Alex Pflanzer was sound asleep when his home’s windows blew out and his wife started screaming.

“I didn’t know what was going on,” he said. “I thought someone was breaking in the house, because the alarm was going off.”

Mr Pflanzer grabbed his gun and started checking the house. Then he noticed the front door was open and saw a reddish glow flickering outside.

“I walked outside and all the houses were on fire,” he said.

There are deadly historical precedents in Indiana if a gas explosion is confirmed to be the cause.

In 1963, 74 people died and more than 400 were injured as a gas explosion ripped through the Indiana State Fairgrounds Coliseum.

Five years later, much of downtown Richmond was levelled by a blast, which killed 41 people.

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