No one was hurt in the 9 a.m. fire.
The natural Christmas tree caught fire after the tenant went to work, police said. The blaze was extinguished by the sprinkler system. However, there was significant water and smoke damage to the second floor unit. The unit below it also sustained significant water damage, police said.
No one was home in either apartment at the time of the blaze.
However, residents of both units will have to find other housing as both units cannot be occupied due to the damage.
Residents are urged to be cautious with holiday decorations.
"Never leave a dry natural tree unattended with the lights on," Greenwich police Lt. Kraig Gray said. "Enjoy them while you are there. And when you are not home, make sure to unplug them."
The fire remained under investigation by the Greenwich Fire Marshal's office.
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