The Morris County Fire Wire Facebook page reported that the 911 caller's son set the Mendham Avenue fire around 3 p.m.
Morris Township firefighters were joined by their colleagues from Morristown, Morris Plains, Madison, Mendham and Cedar Knolls.
The blaze left the house uninhabitable, according to Morristown Green.
The Morris County Prosecutor's Office and local authorities were investigating the cause, Morristown Green reported.
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