Police are hoping to find a man who police said was seen near the fire at 12 South Olney Street earlier this week and took off running when police saw him watching the fire.
According to a police report, Johnston Firefighter Patrick Brockway saw the man, described as white and wearing a black short sleeved shirt, standing behind the fence on the north side of the house.
The man reportedly "took off" across Route 6 as soon as he made eye contact.
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Brockway did not get a clear look of the man's face because he was busy fighting the fire.
Johnston Police officers responded immediately to Route 6 in the hopes of finding the man, but were unable to locate him.
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Firefighters still did not determine a cause as of Monday and planned to use a K9 arson dog to help determine the cause.
The house has since been condemned.
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