TUCSON, Ariz. — The sheriff leading the investigation into the suspected abduction of 84-year-old Nancy Guthrie defended the pace of the probe on Wednesday, citing complex laboratory work, scientific protocols and judicial requirements more than four months after the case began.

Guthrie, the mother of NBC "Today" co-host Savannah Guthrie, was last seen at her home in the Catalina Foothills area north of Tucson on February 2. No arrests have been made, and her whereabouts remain unknown despite a high-profile search involving local, state and federal authorities.

Pima County Sheriff Chris Nanos told local media that the investigation's complexity requires careful adherence to forensic standards, particularly in DNA and digital evidence analysis. "It's just not a detective goes out there, talks to somebody, and we can make an arrest," Nanos said. "This is a very sensitive case, but what really makes it prolonged is we do rely on labs."

Detectives have sent hair samples from Guthrie's home to both a private genetics lab in Florida and the FBI's laboratory in Quantico, Virginia, for advanced testing. Early reports indicated challenges with mixed DNA samples that are difficult to isolate. Digital forensic analysis of video and other electronic evidence also continues.

A spokesperson for the sheriff's office confirmed the investigation remains active. "Forensic analysis of DNA and video evidence remains underway," the spokesperson said. "If and when there is a significant development in this case, it will be shared publicly."

The case has drawn national attention due to Savannah Guthrie's prominence and the circumstances of her mother's disappearance from what appeared to be a secure residence. A combined reward exceeding $1.2 million remains unclaimed for information leading to a........

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