Sheriff's investigators returned to Michael Jackson's Neverland ranch for the second time in two days on Saturday to finish the job, sources told FOX News.

The search began Friday when detectives issued a new warrant and spent more than eight hours looking for evidence, just weeks before the pop star is scheduled to go on trial for child molestation.

Authorities would not say why they returned to the storybook estate Friday, more than a year after dozens of investigators first raided it while they were still drawing up charges against Jackson.

In a statement, the Santa Barbara County Sheriff's Department said only that the daylong search was "part of an ongoing criminal investigation." Spokesman Sgt. Chris Pappas said investigators entered Neverland at 9 a.m. and left about 8 1/2 hours later.

Jackson attorney Thomas Mesereau Jr. (search) had no comment.

Attorneys on both sides of the case are barred from commenting by a court gag order.

Jackson (search) was leaving Neverland when the officers arrived, and did not stay around, said a source close to the family, who spoke on condition of anonymity.

Jackson, 46, was charged in December 2003 with molesting a boy and plying him with alcohol. His trial is set to begin Jan. 31.

A new search so late in the proceedings is very unusual, said a former federal prosecutor who has been following the case.

"It may mean that the witnesses they are preparing for trial now are remembering things at the ranch that they did not mention before," said Laurie Levenson, a professor at Loyola Law School. "They may want to follow up on how certain things looked."

However, she said the search could also be connected to a dispute that has been going on between the prosecution and defense over the sharing of evidence. The defense has been resisting turning over material to the prosecution.

Levenson said if the search yields any physical evidence, it could be of dubious value. "At this stage, if they found anything, if I were Jackson's folks I'd say it was planted. So I'm not so convinced how valuable this would be," she said.

The late-stage search could also help the defense win a delay, Levenson said. "How do you go to trial in a case when they are still serving search warrants?" she said.

Neverland, set amid the emerald hills and horse ranches about 100 miles northwest of Los Angeles, was first searched in November 2003 by at least 60 investigators from the Sheriff's Department and district attorney's office.

The theme park-like estate has a mansion, zoo, bumper cars, a merry-go-round and Ferris wheel. Jackson hosted many children's parties there.

Fox News' Adam Housley and The Associated Press contributed to this report.