Jermaine Jackson: Mother Katherine is fine, not missing - USA TODAY

Michael Jackson's family is involved in a messy dispute with matriarch Katherine's advisers, and tension reached a new level overnight when her nephew reported her missing.

However, her son, Jermaine, tweeted after the initial panic:

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

He subsequently added:

This is our mother and her health is paramount. We are not inventing or plotting anything. We are following doctor's advice. Period.

The latest development comes after a letter signed by four of the late pop star's siblings -- Jermaine, Janet, Rebbie, Randy and Tito -- was made public Wednesday. It accused Michael's estate executors John Branca and John McClain of conspiracy and abusing their 82-year-old mother.

On Wednesday, estate spokesman Jim Bates said in a statement to CNN: "We are saddened that false and defamatory accusations grounded in stale Internet conspiracy theories are now being made by certain members of Michael's family."

Today, CNN is reporting that Katherine Jackson's lawyer, Sandra Ribera, had said that her client left her California home on July 15, to fly to Albuquerque to attend a Jackson brothers concert. She was traveling with Rebbie.

Ribera told CNN that when Michael's 14-year-old daughter, Paris, called to talk to Katherine over the past several days, she was told each time she could not speak to her.

Katherine's nephew, Trent, reported her missing to authorities last night. TMZ has a statement from authorities that says as a result of the report, the Los Angeles County Sheriff's Department is attempting to contact Katherine.