Katherine's nephew, Trent, reported the 82-year-old matriarch missing late Saturday night, saying she had not been heard from in a week.
Her granddaughter, Paris Jackson, took to Twitter to share her concern over her grandmother's supposed disappearance, writing, "Yes, my grandmother is missing. I haven't spoken with her in a week I want her home now."
But, Katherine's son Jermaine Jackson chimed in Friday night prior to the missing persons report, tweeting, "I want to reassure everyone (inc all sudden medical experts) that Mother is fine but is resting up in AZ on the orders of a doctor, not us. This is our mother and her health is paramount. We are not inventing or plotting anything. We are following doctor's advice. Period."
Earlier Sunday, he Los Angeles County Sheriff's Department told E! News Katherine was with family.
"Katherine Jackson is reportedly with family members," the Los Angeles County Sheriff's Department told E! News. "Late Saturday night, a different family member reported that he was unable to speak with her and is concerned for her well being. Deputies are continuing to make efforts to reach her and ask that she contact the Malibu/Lost Hills Sheriff's Station of the Los Angeles County Sheriff's Department."
But by the evening, officials confirmed the case was serious enough to be turned over to the missing persons unit that works out of sheriff's homicide bureau. The detective who took control of the investigation is working on contacting family members.
Katherine's attorneys also chimed in Sunday, further explaining the concern of the family, saying she was gearing up to go on a road trip and watch her sons perform on their Unity Tour, but a doctor was brought to her home and ordered her to fly instead. She was reportedly told that the doctor was from the office of her longtime physician.
"During what was to be a brief trip, Mrs. Jackson left her son Michael's children, of whom she is guardian, in the care of her adult grandsons," her attorneys said in a statement to E! News. "Knowing that their grandmother has never gone more than 24 hours without checking in with them when she travels, her grandchildren grew concerned after they failed to hear from her and contacted family members asking to speak to her."
"Michael's children were told by family members who were allegedly with Katherine Jackson that their grandmother was not available to speak to them. Mrs. Jackson did not attend any of her sons' concerts, which she had been looking forward to for some time. Moreover, Katherine Jackson's longtime physician recently confirmed that his office did not send a doctor to Mrs. Jackson's home last weekend before she left on her trip."
News of Katherine's supposed disappearance comes just a few days after some of Michael's siblings accused the two men overseeing his estate of fraud over the late pop icon's will.
The will named only Michael's children and Katherine as beneficiaries.
The police suspect no foul play in Katherine's missing persons case, according to People.
(Originally published July 22, 2012, at 1:14 p.m. PT)
—Reporting by Baker Machado and Holly Passalaqua