Police received a 911 call at about 3:30 p.m. from a mother reporting that her 5-year-old son and a 7-year-old daughter disappeared from their home in Central Islip, said Detective Sgt. Edward Fandrey of the Suffolk County police homicide squad.
While searching the neighborhood, an officer spotted a shoe floating in a next-door neighbor's aboveground pool, which was uncovered and contained blackish water, Fandrey said.
Officers jumped into the 4-foot-deep pool and discovered the unconscious bodies of Ralph Knowles and Sharon Knowles. The brother and sister were taken to Southside Hospital, where efforts to resuscitate them failed, Fandrey said.
The pool is surrounded by a deck. Both are sunken into the ground and surrounded by a low, wooden fence.
Fandrey said the pool's owner had been cited by the town for improper fencing.
"The exposed side of the stockade fence was facing out, instead of the smooth side," he said, adding that the slats made it easier to climb over the shared fence.
Telephone calls to numbers listed for the addresses of the victims and the pool's owner went unanswered Sunday night.
The home where the children lived is owned by a nonprofit that provides housing to homeless families, Newsday reported.
The children's uncle, Henry Valentine, 32, of Jamaica, Queens, told the newspaper that the childrens' mother, whom he identified as Tia Knowles, was "devastated."
"She's not doing good at all," he said.