Venomous Portuguese man-of-wars were spotted Wednesday in the waters off the Hamptons and Montauk, according to reports from the Long Island Coastal Conservation and Research Alliance.
The sightings came after two children were stung Tuesday on Fire Island.
The new reports come from Montauk and Tiana Beach in Hampton Bays, said Christopher Gobler, who leads the alliance, an environmental research group at Stony Brook University.
Man-of-wars, a colony of organisms with long tentacles and a venomous sting, were seen in Cherry Grove and Fire Island Pines, according to Elizabeth Rogers, a park ranger for the Fire Island National Seashore.
On Tuesday, a 7-year-old boy was stung on the hand in Kismet and a 4-year-old boy was stung in Davis Park, officials said.
A third person was stung in Davis Park but declined medical assistance.
Usually found in tropical waters, the dangerous jellyfish can be carried by wind and currents into the North Atlantic when the water is warm and the winds are out of the southwest.
Earlier this week, dozens were spotted along the Jersey shore.
In 2013, about 50 were spotted beached along the East End.