“TODAY” co-anchor Savannah Guthrie on Tuesday announced her family is offering a reward of up to $1 million for the recovery of her 84-year-old mother, Nancy Guthrie, who disappeared more than three weeks ago.

“Someone knows how to find our mom and bring her home,” Savannah Guthrie wrote in a caption accompanying a video published on Instagram just before 9 a.m. Tuesday.

In the video, a visibly emotional Savannah Guthrie urged the public to keep her mother in their thoughts.

“Please keep praying without ceasing,” she said. “We still believe. We still believe in a miracle. We still believe that she can come home, hope against hope. As my sister says, ‘We are blowing on the embers of hope.’”

“We also know that she may be lost,” she added. “She may already be gone.”

By Tuesday night, 12 hours after the family reward was made public, more than 750 calls had come in to the FBI’s tip line, a senior law enforcement official told NBC News.

The Guthrie family plans to donate $500,000 to the National Center for Missing & Exploited Children. “We know there are millions of families that have suffered with this kind of uncertainty,” Savannah Guthrie said.

Michelle DeLaune, the chief executive of the National Center for Missing & Exploited Children, told “TODAY” that the Guthrie family’s “very generous” donation will help many families.

“It’s a tremendous opportunity to raise the visibility of many cases that otherwise would not be receiving this type of attention,” DeLaune said.

The Guthrie family was prepared to offer a cash reward from the beginning of the investigation, but they were advised that doing so might overwhelm the infrastructure set up to field leads, according to a source close to the family.

The family decided to offer the reward after careful consultation and coordination with law enforcement, the source said.

The reward does not hinge on an arrest or prosecution, only Guthrie’s recovery, the source said, and the $1 million can be split if there is more than one valid claim.

Former FBI supervisor Jason Pack told “TODAY” that the Guthrie family’s reward suggests a strategic pivot.

“There are some people who were close to what happened, that know what happened, that now have a decision to make, and that decision was really, really ratcheted up by this reward that Savannah and her family offered,” Pack said.

The Pima County Sheriff’s Office said early on that investigators believe Guthrie was “taken from the home against her will, possibly in the middle of the night and that includes possible kidnapping or abduction.”

Authorities have not identified a suspect in the case, though the FBI released doorbell camera images and videos of an armed and masked man outside Guthrie’s house on the morning she disappeared. (Two law enforcement sources said Monday that one of the images was captured earlier.)

All members of the Guthrie family have been cleared as possible suspects, Pima County Sheriff Chris Nanos previously said, adding that to “suggest otherwise is not only wrong, it is cruel.”

“The Guthrie family are victims, plain and simple,” Nanos added.

Savannah Guthrie and her siblings have posted a series of Instagram videos since their mother went missing. In some of the videos, Savannah Guthrie made direct appeals to her mother’s possible captor.

The FBI is offering a $100,000 reward for any information that leads to Guthrie or to an arrest, and an additional $102,500 reward is being offered through Tucson Crime Stoppers, known locally as 88-CRIME.

A federal official earlier had said that the Guthrie’s reward offer was likely to generate tips. “We don’t need another thousand calls. We need one. Money can erode a lot of allegiances,” the senior law enforcement official said.

Supporters of the Guthrie family have left flowers and handmade posters outside her home. In one sign seen by NBC News early Tuesday, an unidentified person directly addressed Guthrie’s possible kidnapper.

“Unintentional things happen, and we get that,” one part of the sign said. “Life is made up of choices. Please make the right one now.”