ANDOVER, Mass. -- Police investigators are searching for clues to determine what led to the death of Wellesley teenager Elizabeth Mun, who was found unconscious in a frozen pond early Sunday.

An autopsy will be performed later this week to find the exact cause of the Concord Academy student's death, the district attorney's office said.

Mun, 16, of 204 Grove St., Wellesley, was reported missing by her friends several hours after she left a sleepover party at 58 Williams St. on foot about 5 a.m.

Police said the parents who own the house were not home during the party.

Mun's friends searched for her before reporting her disappearance to police just before 7 a.m. The home was being treated as a crime scene.

Crews used a state police helicopter to search the area near Routes 28 and 133 in Andover for several hours before locating the girl at about 11 a.m. in a pond behind Warwick Circle, Andover police Lt. James Hashem said.

He said police were looking into whether alcohol was consumed at the Williams Street gathering.

“We’re trying to find out what she was doing prior to leaving the house, when she was at the house, and what she did after she left the house,” Hashem said. “Everything is open to investigation right now.”

The girl was taken by helicopter to Children's Hospital, where she later died about 5:30 p.m.

Concord Academy released a statement about the student's death Sunday night, saying the school was devastated by the teen's death.

“She was an independent thinker with a finely tuned sense of humor, and we are all mourning her loss,” Pamela J. Safford, associate head for enrollment and planning at Concord Academy, said.

Alumni who attended the elite preparatory school include Caroline Kennedy and Harvard University's current president, Catherine Drew Gilpin Faust.

A Plainville, Mass., teenager, Taylor Meyer, 17, died last fall when she wandered away from a drinking party in Norfolk and drowned in a marsh.