The disclosure came after another concerned family member officially reported her missing Saturday night amid a dispute over the estate of her superstar son.
A person familiar with Katherine Jackson's whereabouts said she is with her daughter Rebbie in Arizona and following a doctor's orders to rest. The person was not authorized to speak publicly and spoke on condition of anonymity.
The 82-year-old Jackson family matriarch was reported missing by a relative on Saturday night. Sheriff's officials later said they believe she is in Arizona with a relative, but they were still trying to establish contact with her.
Katherine Jackson's whereabouts caused concern for some family members in recent days, and her granddaughter Paris Jackson issued a frantic plea on Twitter early Sunday.
"I haven't spoken with her in a week I want her home now," she posted from her Twitter account. She also tweeted a number for people to contact in case they saw her grandmother.
Katherine Jackson also hadn't been in contact with her attorneys, who worked Sunday to learn more information about her whereabouts and why she had suddenly become incommunicado, including with her grandchildren.
"First of all, let's hope that this is all just a big misunderstanding and a totally benign situation," her attorney Perry Sanders Jr. said Sunday. "Assuming that she did actually leave on doctor's orders, no matter which doctor, it has certainly created an absolutely irregular situation whereby she has been out of contact with her grandchildren."
The mystery of Katherine Jackson's whereabouts was compounded by a recent visit from her son's former physician, Dr. Allan Metzger, who examined her July 14 after being brought to her home in Calabasas by someone close to the family, said Katherine Jackson's attorney Sandy Ribera.
The visit came one day before Katherine Jackson was scheduled to depart on an RV trip to the Southwest to watch her sons perform at concerts. The elder Jackson never made any of the shows and Metzger apparently told her not to take the trip, Ribera said.
Metzger is not Katherine Jackson's primary physician and her regular doctor wasn't aware of his house call until concerns about Katherine Jackson's whereabouts were raised, Ribera said.
A phone message left for Metzger at his Beverly Hills practice was not immediately returned Sunday.
Metzger treated Michael Jackson earlier in his career and met with the singer once in the months before he died. Defense attorneys for the physician convicted of killing the pop superstar called him as a witness to try to show the singer was attempting to obtain a powerful anesthetic for home use.
Despite being a defense witness, Metzger aided prosecutors by telling jurors that he refused Jackson's request and warned him of the risks.
Paris Jackson referenced Metzger's visit in a tweet early Sunday, writing, "the same doctor that testified on behalf of dr murray saying my father was a drug addict (a lie) is caring for my grandmother... just saying."
Conrad Murray was convicted of involuntary manslaughter for the June 2009 propofol overdose death of Jackson at age 50.
The family drama unfolded days after it was revealed that some of Katherine Jackson's children had written a letter to the executors of Michael Jackson's estate, alleging his will, which left his fortune to his children, his mother and charity, was a fake.
The undated letter, signed by Janet, Randy, Tito, Rebbie and Jermaine Jackson, claimed Katherine Jackson was being manipulated by the executors, John Branca and John McClain, her health had been affected, and she suffered a mini-stroke.
The legitimacy of the letter was confirmed by Randy Jackson on Twitter, and Janet Jackson retweeted his post.
The estate has denied the accusations. Katherine Jackson obtained permission from a judge to probe the validity of her son's will, but never pursued the matter in court.
On Friday, Jermaine Jackson tweeted that his mother was resting on the orders of a doctor in Arizona.
"This is our mother and her health is paramount. We are not inventing or plotting anything," he posted. "We are following doctor's advice. Period.""
Katherine Jackson has been caring for Paris, Prince Michael and Blanket Jackson since their father's death. It was unclear who is taking care of the children in her absence.