The pacemaker of Savannah Guthrie’s mother suddenly stopped syncing with her Apple Watch — what happened?

Nancy Guthrie’s pacemaker stopped syncing with her Apple devices predawn Sunday, a Tuesday report said as the search for the mother of NBC News star Savannah Guthrie reached into a third day.

The implanted medical device lost contact with the Apple products belonging to the 84-year-old grandmother around 2 a.m., a law enforcement source told Fox News.

When authorities reached her Arizona home hours later, around noon, Nancy’s phone and Apple Watch were still inside the house, the source said.

The disturbing revelations come as Pima County Sheriff Chris Nanos said on MS Now that the ongoing search is becoming more investigative.

“The air and ground searches … you’ll see that slow down,” he said Tuesday morning. “Those things are going to slow down, we’re pushing more to the investigative side of this.”

The top cop said more DNA and video footage evidence is expected to come in.

“She is an 84-year-old woman who went to bed, and sometime in the middle of the night, she was removed from that home and now here 48 plus hours, and this lady needs her medication,” he said. “So it’s not good.”

The Pima County Sheriff’s Office was expected to address reporters around 11:30 a.m. local time to provide an update after previously telling The Post just hours earlier that there were no media appearances planned for Tuesday.

Law enforcement previously said officials believe Nancy was possibly kidnapped or abducted from her home.

Nanos, with the FBI by his side, addressed reporters during a hastily-called press conference Tuesday that offered no insight into the concerning disappearance.

He said authorities didn’t have a suspect – or even know how many people might’ve been involved in the high-profile missing person case.

“We do believe Nancy was taken from her home, against her will, and that’s where we’re at,” Nanos said as he stressed it was also unclear if this was a targeted crime.

He also declined to narrow down the time she might’ve disappeared, only noting she was dropped off at her home around 9:30 p.m. Saturday and was gone by the time reached her home late Sunday morning.

“On behalf of our family, I want to thank everyone for the thoughts, prayers and messages of support,” she said in a statement provided by NBC.

“Right now, our focus remains on the safe return of our dear mom. We thank law enforcement for their hard work on this case and encourage anyone with information to contact the Pima County Sheriff’s Department at (520) 351-4900.”