Pop star Michael Jackson, shown in November 2007, was under investigation by the FBI for at least 10 years before he faced child molestation charges in 2003. (Danny Moloshok/Associated Press)

Police in the southern California city where pop star Michael Jackson stood trial on child molestation charges called in the FBI because they feared he might become a terrorist target.

The Santa Maria police were afraid the court case would be a "soft target" for terrorism, according to documents released by the FBI on Tuesday after a freedom of information request.

Federal agents had been looking into Jackson's alleged involvement with young boys for nearly 10 years before that 2003 arrest, the documents show.

They also had looked into death threats against Jackson by a man obsessed with his sister, Janet, as far back as 1992.

The FBI released 333 pages of documents related to the late pop singer on Tuesday that date from 1992 to 2005.

At the molestation trial, FBI eventually concluded there was little risk of terrorism, although they noticed that a Nation of Islam follower and New Black Panther Party member, both unnamed in the files released, sat in the gallery in the early part of the trial. Jackson was eventually acquitted of all charges.

The files show FBI had been tipped off by their London, England, office in 1993 of an alleged inappropriate involvement between Jackson and an underaged male. Over the next 10 years, they made several investigations of the pop star, none of which led to charges.

Death threats against Jackson, president

Federal investigators assisted Santa Maria police in combing through computers at Neverland, Jackson's California home, in the molestation case. They also helped customs officials investigate a video suspected to be child pornography.

Neither of those investigations yielded substantive evidence, according to the documents.

FBI also interviewed two former Neverland employees in the Philippines over allegations of Jackson fondling young boys.

But the files released Tuesday contain no major revelations about Jackson's private life and the bureau apparently never developed any solid evidence against him.

They did include death threats against Jackson, then President George H. W. Bush and mob boss John Gotti by Frank Paul Jones, who allegedly was obsessed with Janet Jackson.

Jones was convicted in 1993 in relation to a letter that states: "I decided that because nobody is taking me serious, and I can't handle my state of mind, that I am going to Washington, D.C., to threaten to kill the president of the United States, George Bush."

The letter later says, "Michael [Jackson] I will personally attempt to kill, if he doesn't pay me my money."

Jones was arrested June 22, 1992, after trespassing in the driveway of the Jackson family compound in Encino, Calif.

Jackson, the singer known as the King of Pop, died June 25 at age 50. His death was ruled a homicide and police are still investigating.

With files from The Associated Press