Cadaver dogs searching for a Massachusetts girl who disappeared 23 years ago have zeroed in on a small patch of parkland close to where an anonymous tipster recently suggested authorities check.

A private investigator leading the search for 14-year-old Melanie Melanson told that three dogs were alerted to a small area of land during Saturday's search of Middlesex Fells Reservation. The girl was five days shy of her 15th birthday when she vanished in October 1989, after attending a party with friends in a wooded area near the Woburn-Stoneham town line. Authorities believe the girl was killed, but her body has never been found and no suspects have ever been named in the case.

Michael Garrigan, a private investigator who has worked on the case since 1991, said he recently received an anonymous tip from a man in New Hampshire. The anonymous caller directed authorities to search nearby Middlesex Fells Reservation in Stoneham, where he said one of the teenage boys last seen partying with Melanson was spotted later that night. During Saturday's search, officers from the Woburn Police Department observed as Garrigan worked with the police-trained dogs.

Garrigan said at least three dogs picked up on an "area of interest" Saturday during their search of the 2,500-acre park. He described the area as a 15-by-15 foot square patch of land that would have been "very accessible" in 1989. He said the next step will likely call for investigators to use a Ground Penetrating Radar, or GPR, to detect possible human remains. 

Melanie, then a freshman at Woburn High School, was the youngest attendee at the party on Oct. 27, 1989, in a wooded hangout popular to area teenagers. In the hours immediately following her disappearance, authorities suspected the girl may have run away, but later concluded that she was likely killed.

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"We don't believe she ran away. We believe that she's deceased," Jessica Pastore, a spokeswoman for the Middlesex County district attorney's office, told last week. 

"We're hopeful that we can find Melanie and give her the proper burial that she deserves," said Pastore, adding, "We know who was with Melanie the night she disappeared."

The girl's family has said she was last seen with two teenage boys in the early morning hours of Oct. 28, 1989, according to local media reports.

Garrigan said he believes that if Melanson's remains are in Middlesex Fells Reservation, "my gut feeling is that she was not alive" when she was taken out of the woods.

The latest search for the girl comes after dogs detected a positive hit for human decomposition last year in an area close to where she was last seen.

"Everyone came out of that woods but her," said Garrigan, "And I’m confident something is in that ground or was in that ground."

"I’m not going to stop looking until I find this girl," he said. "I don’t think any family should go this long without closure."

A $5,000 reward is being offered for any information leading to Melanie Melanson's remains. Anyone with information on her disappearance is urged to contact the Woburn Police Department at 781-933-1212 x853 or State Police assigned to the Middlesex district attorney's office at 781-897-6650.