The Pima County Sheriff’s Office says it could take up to a year to identify a potential DNA match in the disappearance of Nancy Guthrie, the mother of “Today” show anchor Savannah Guthrie.

Nancy Guthrie has been missing for three weeks. Authorities have not identified a suspect or developed confirmed leads regarding her whereabouts. The Federal Bureau of Investigation said she was last seen Jan. 31 at her residence in Tucson’s Catalina Foothills neighborhood. Investigators consider her a vulnerable adult due to mobility issues, a pacemaker, and the need for daily heart medication.

Mixed DNA recovered at the scene has raised hopes of a breakthrough. Pima County Sheriff Chris Nanos told NBC News that some of the DNA does not belong to Nancy Guthrie, her family members, or anyone employed at her residence. However, he acknowledged there are technical challenges with the sample.

“As with any biological evidence, there can be challenges separating DNA,” the sheriff’s office said in a statement, adding there are currently no updates on the testing process.

Experts interviewed by NBC News explained that mixed DNA samples can complicate forensic analysis. Genetic genealogist Coleen Fitzpatrick said that if a sample contains a high proportion of the missing person’s DNA — for example, 90% — it may be difficult to isolate enough markers from the remaining portion to identify another individual. Conversely, a more evenly mixed sample can also present separation challenges.

CeCe Moore, chief genetic genealogist at Parabon, a Virginia-based forensic lab, noted that ancestry can influence how quickly a match is found. She said individuals with deep U.S. roots and primarily northwest European ancestry are often identified more quickly because most genetic databases contain similar profiles. Cases involving individuals with more recent international ancestry may take longer.

Sheriff Nanos emphasized that advancing forensic technology could help resolve current limitations. “Technology is moving so fast,” he said, suggesting improvements in DNA analysis could yield clearer results in weeks, months, or potentially up to a year.

For now, investigators continue to await lab findings as the search for Nancy Guthrie remains ongoing.