The actress, who was away when the incident took place, said she is in "absolute shock" to learn about the drowning of a 21-year-old man.
Moore's caretaker threw a party and invited the victim while the 52-year-old "Very Good Girls" actress was out of town.
The caretaker and others allegedly went out at some point leaving the victim behind and when they came back the victim was already at the bottom of the pool.
Law enforcement sources said the police discovered the body on early Sunday at the bottom of the pool, reported TMZ.
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Neither Moore nor her kids were present at the time, but a neighbour said the actress' kids have been staying at the house for weeks and have been throwing "parties every day, day and night."
There was no foul play and police are still investigating the case. Moore's representative hasn't commented on the issue yet.
Reacting to the shocking news, Moore called it an "unthinkable tragedy".
"I am in absolute shock. I was out of the country traveling to meet my daughters for a birthday celebration when I got the devastating news," she said in a statement.