SCARSDALE ? A video of two high school girls engaged in a sexual encounter as boys coax them into more intimate activity has been circulating in the Scarsdale school community, drawing the attention of authorities who are investigating whether a crime took place.

In the 18-minute homemade video, the girls are egged on by the videographer and the onlookers, who make coarse sexual comments and repeated references to drinking beer. As the sexual activity intensifies, one girl becomes reluctant, saying "stop" and "no" numerous times and pushing the other girl's hands away as the group pressures her into continuing. The activity involved groping, kissing and partial nudity.

The video, apparently made at an unsupervised party in Scarsdale during spring break, was ultimately distributed among students via the Internet.

A parent learned of the video and notified school officials last week, a spokeswoman for the Scarsdale district said. The officials alerted Scarsdale police.

The police said they are investigating the matter with the Westchester County District Attorney's Office.

"We are working hand in hand on this matter (with the D.A.'s Office), but we also do not have a victim who has necessarily at this time come forward," police Lt. Bryant Clark said. "We are trying to speak with everybody who was at the party."

Clark said that there was not "a clear portrayal of criminal activity" on the video and that the participants all appeared to be minors.

"The question for the Police Department and the District Attorney's Office is, 'Is there some kind of violation of a statute?' " Clark said. "Viewing things on a tape is a small part of a complete investigation, which also involves interviewing people and talking to any possible victims. ... This is an active investigation that has to go a lot farther than just viewing what was on the tape."

District Attorney Jeanine Pirro's office was looking into the matter, said spokeswoman Ann Marie Corbalis, who declined to comment further.

Clark, the police lieutenant, encouraged anyone with information that could help the investigation to come forward.

"If anybody ever does feel that they are ? and I can't say it in any stronger possible terms ? a victim of some sort of possible sexual activity ... please contact the Police Department, because that's something we're very interested in," he said.

The existence of the video was common knowledge among dozens of students interviewed in the past two days. Many said they had seen it; others said they had heard about it.

Junior Jennifer Salant, 17, said most students she spoke with were disturbed by the incident, and she chose not to view a copy that was e-mailed to her.

"It's sad that something this awful could happen here or anywhere," said Salant, co-editor of the high school newspaper. "It's bad that the incident occurred, and the fact that it was spread and sensationalized, and it became a topic of conversation is disgusting and upsetting. There were individuals who took pleasure in embarrassing these girls by spreading it. That is the even sadder part."

"I'm appalled," said Fletcher Marks, 18, who is graduating from Scarsdale High School tomorrow. "It was a disgusting display of adolescence."

Marks said he hadn't watched the video, though some of his friends had seen it.

Some students feared the incident would unfairly depict their school and the upscale Westchester community in a poor light.

"It's weird and it's awful, but in no way do I think it's a reflection of Scarsdale," said senior Jessie Bell, 18.

Many students said they deleted the video from their computers when they heard that police and lawyers were getting involved.

Families of the two girls in the video declined to talk to The Journal News. Efforts to get comments from others involved were unsuccessful. Their names are being withheld by the newspaper because they are minors.

Because the incident occurred off school premises, the school will not discipline any students, district spokeswoman Victoria Free Presser said.

"Our first concern is for the victimized young people in the video," she said. "We have offered counseling services to the families involved. Our main concern is to refrain from doing anything to worsen the situation of these young people."

The school did not address the issue with the student body, although a student said one of his teachers referred to it.

"She said to our entire class on our last day that we shouldn't be doing this at this young an age," freshman Mike Morabito said. "'If you want to do something stupid with your life, don't do it when you're young; you have a whole life ahead of you.' "

The incident follows a number of highly publicized cases involving underage drinking in the region. In 2001, students from Chappaqua's Horace Greeley High School attended a party where parents of a student provided a stripper who performed sex acts. The following spring, a Harrison High School student died after a fight at a beer bash. Later in 2002, dozens of students showed up drunk at a Scarsdale dance.

Advances in digital video technology have led to a nationwide increase in the recording and transmission of imagery depicting minors engaged in sexual acts, said Jack Samad, senior vice president for the National Coalition for the Protection of Children and Families.

"I hear about it all over the country, and the bottom line is that parents are clueless," Samad said. "I used to tell parents to guard their home computers, but now they're giving their kids PDAs, (personal digital assistants) cell phones that take videos, and all kinds of gadgets that they can use with absolutely no supervision ? and these are the kinds of results we're getting."

Samad cited the recent expulsion of a number of students in Oklahoma after a teenage girl photographed her bare breasts with a cell phone in a school restroom, and then transmitted the image to a number of students with the message, "Guess who?," who in turn transmitted the image to several other students.