The girl was taken to the East Patchogue facility for treatment after police responded to the home of John and Stacie Butler at 81 Old Broadway at about 1:33 a.m. Sunday, police said.
When police arrived, they said, they found more than two dozen teenagers -- some visibly intoxicated -- in an apartment separate from the main house.
Witnesses said large amounts of vodka had been consumed, and officers also saw shot glasses and evidence of a game of beer pong, police said.
Police said the Butlers' daughter, 16, had invited friends over after a junior-class banquet at St. Anthony's High School in South Huntington.
Other teens who did not know the Butlers also were at the party, police said.
The Butlers, both 54, were arrested on misdemeanor charges of endangering the welfare of a child and were released after posting bail.
Police said the girl who became sick is not the couple's daughter.
Suffolk County's social-host law -- which targets adults who allow minors to drink at their homes -- did not apply to this arrest because officers did not witness drinking, a police spokeswoman said.
Neither police nor St. Anthony's principal, Brother Gary Cregan, said Monday whether the Butlers' daughter or the girl who became ill are students at the school.
A police spokeswoman said police did not know, and Cregan said he was declining to identify the girls as a students because of his own loyalty in dealing with minors. "I'm totally looking to protect" children, he said.
However, Cregan did say he was meeting with the Butlers on April 9 -- which seems to indicate their daughter is a student -- and he said the high school has a policy that strictly forbids underage drinking.
Cregan would not elaborate, citing the ages of the girls involved and again stressing he "was carefully not answering any questions."
But in a prepared statement released by St. Anthony's, Cregan reminded parents of the school's policies and also said, "While St. Anthony's cannot be responsible for monitoring students once they are off the property, we are disappointed that such an incident occurred. The matter will be addressed internally."
Cregan said that in "extreme situations" where students had violated school policy some parents were either asked to withdraw the student from the school or the student was expelled.
"That may or may not apply in this situation," he said.
With Jennifer Barrios