Deadly Cleveland Fire Ruled Arson

CLEVELAND -- Investigators have determined that a house fire that killed nine people in Cleveland last month was deliberately set.

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IMAGES: 9 Die In Fire

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The great-grandmother of one of the victims said whoever set the blaze "should be buried."

Officials have ruled the fire arson. The fire broke out during a sleepover birthday party for a teen.

Test results have confirmed the presence of accelerant in the blaze, but authorities say they don't know who set the fire. Mayor Jane Campbell told Cleveland TV station WEWS that investigators kept probing because so many people were not able to get out of the home.

"There was a piece of it that just didn't make sense," Campbell said. "How could that many able-bodied, healthy people not be able to get out?"

She said they continued to collect samples and finally found the accelerant.

Campbell said it was important for officials to tell the family before they heard it from the media.

She said the investigation will take a different turn to try to figure out who had motive and opportunity.