Nancy Guthrie Cold Case Gets Revival as FBI Analyzes Key DNA Evidence

The hunt for Nancy Guthrie in her cold case may have just hit a turning point ... because the FBI is using new technology to zero in on DNA evidence.

Law enforcement sources tell TMZ that agents are analyzing what could be a crucial sample recovered from the 84-year-old’s Tucson, Arizona home ... and it’s already been sent through a private lab working with the Pima County Sheriff's Department before landing in federal hands.

This is the same DNA evidence that was recovered from Nancy’s home earlier in the probe. But here’s the catch ... the DNA isn’t clean. Investigators say it’s a mixed sample from multiple people, meaning it’ll take time to separate and figure out what actually matters.

Sheriff Chris Nanos has already warned it might take time to fully process. He recently told a Neighborhood Watch group it could take another six months to sort through the DNA -- separating the strands and isolating exactly what investigators need.

Still, the feds are throwing their latest tech at it, hoping it finally points them to whoever abducted Nancy back on Feb. 1. Roughly two dozen investigators from the Pima County Sheriff's Department and the FBI are still actively working the case.

As for Savannah Guthrie ... she’s been devastated during her search for answers. In a tearful interview last month with fellow "TODAY" anchor Hoda Kotb, she apologized to her mom and even questioned if she somehow played a role -- though she admitted the family still has no real answers.