The unidentified girl was found Saturday afternoon by emergency workers and pronounced dead at Trinitas Regional Medical Center in Elizabeth.
It was not immediately known who placed the 911 call or whether anyone else was with the girl at the time.
The pool was about 2 feet deep and 10 feet in diameter.
A man who says his mother owns the house tells The Star-Ledger of Newark (http://bit.ly/QU3rEr) that his brother bought the pool for a birthday party and emptied it after each use because it didn't have a filter.
There have been 23 drownings this summer in New Jersey, according to the newspaper, mostly in Ocean and Cape May counties.
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