A heavy law enforcement presence descended on a normally quiet stretch of woods in Nassau County Wednesday, as federal and local agencies launched a large-scale investigation inside the Underhill Preserve in Jericho.

FBI and Homeland Security agents were seen combing through the wooded area near Cedar Swamp Road throughout the day. The Nassau County Medical Examiner’s Office was also on site.

By nightfall, law enforcement officials had cleared the area, but not before raising serious concerns among parents and staff at nearby Jericho High School.

"Oh my God, it’s so scary. My daughter goes to school here," said Gina Raso, a Jericho parent.

“It’s definitely frightening to see, especially by a school building,” added Michelle Gargiulo, a teacher at Jericho High School.

While federal officials confirmed an investigation is underway, they have not provided any details about what prompted the activity or what they may have found.

In addition to the FBI and Homeland Security, New York State Police deployed a K-9 unit, and Nassau County Police Crime Scene investigators were also present at the scene.