Authorities received an emergency call just before 3:30 p.m. EDT about a 7-year-old girl and 5-year-old boy missing from a home in Central Islip, WABC-TV, New York, reported.
Police searched the area and found the children in the water behind another home.
The children were taken to South Side Hospital, where they both were pronounced dead, the TV station said.
WCBS-TV, New York, reported the children had been missing from a home on Naples Avenue, while the pool where they were discovered was behind a home on nearby Half Mile Road.
Wisconsin business offering 'therapeutic cuddling' forced to close
Costly malfunction causes beer flood at Boston-area brewery