In an exclusive report from OK! Saturday, the source says the unidentified fan has repeatedly sent disturbing packages to Spears at a Los Angeles home, albeit not one owned by the "Toxic" singer.

"It started about six weeks ago with just letters being sent once a week," the source said. "And then it quickly escalated to larger packages that now arrive two to three times a week -- always to the same LA address, but never to one of Britney's homes."

According to the source, the packages are filled with a battery-operated sex toy and sexually explicit notes detailing the fan's obsessive fantasies regarding the pop singer.

The magazine said Spears' security team has been made aware of the packages, which also come with a photograph of a man who may be the obsessed fan.

The singer's security team reportedly has handed the packages over to the FBI, which is now investigating the matter.