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Late Wednesday afternoon, Johnston County Sheriff Steve Bizzell said DNA tests confirmed that some of the remains, which were found under the house and beneath a shed of Bobby and Louise Pollard over the weekend, were those of 16-year-old

Robin Leigh Clark

, who disappeared in 1997.

Bizzell said that LabCorp, a private laboratory in Research Triangle Park, matched DNA extracted from some of the body parts with DNA from Clark's mother.

Clark was identified as a possible victim after authorities linked Bobby Pollard to the death of Caesar Ortiz, who also disappeared in 1997. Authorities said Ortiz and Clark, who were involved with one another, lived for a period of time with the Pollards before their disappearance.

Authorities are still waiting for medical records from Ortiz's family in Mexico, which could also help them in the case. Investigators said Sunday they recovered more than one set of body parts from the farm.

Meanwhile, investigators spent a fifth day searching for clues and tagging potential evidence at the Pollards' farmhouse in Selma.

"If there's bone fragments or any other evidence that would be conclusive to this investigation, of course if it's there, we want to find it," said Johnston County Sheriff Steve Bizzell.

Initially, investigators had hoped to finish their collection of evidence Wednesday, but now expect to be at the scene for a few more days.

Authorities have yet to comment on a motive as to why the dismembered parts were at the farm or about the tip that led investigators to the farmhouse on Saturday.