Savannah Guthrie, the co-anchor of "Today," is hoping anyone with information about her missing mother comes forward as the case enters its second week.

Guthrie called the ordeal a "nightmare," in a video on Instagram.

"I just want to say, first of all, thank you so much for all of the prayers and the love that we have felt, my sister and brother and I," Guthrie said. "And that our mom has felt.

"Because we believe that somehow, someway, she is feeling these prayers," Guthrie said. "And that God is lifting her even in this moment and in this darkest place."

Investigators believe Nancy Guthrie was taken against her will last weekend from her home just outside Tucson.

DNA tests showed blood on Guthrie's front porch was a match to her, Pima County Sheriff Chris Nanos has said.

Guthrie said she believes her mom is still alive.

"We need your help," Guthrie pleaded in the video. "Law enforcement is working tirelessly around the clock trying to bring her home, trying to find her."

"She was taken and we don't know where," Guthrie added. "I'm coming on just to ask you, not just for your prayers, but no matter where you are, even if you're far from Tucson, if you see anything, if you hear anything, if there's anything at all that seems strange to you, that you report to law enforcement."

"We are at an hour of desperation," Guthrie concluded.

Detectives and agents continued to perform follow-up work at multiple locations as part of the investigation, according to an email from the Pima County Sheriff's Department in Arizona.

The agency said in the email to media that it would not yet provide details about that work.

Authorities say they have growing concerns about Nancy Guthrie's health because she needs daily medication. She is said to have a pacemaker and has dealt with high blood pressure and heart issues, according to sheriff's dispatcher audio on broadcastify.com.

The Associated Press contributed to this report.

• Investigation Continues as Guthrie Family Pleads for Mother's Return
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