Further details have emerged about the contents of the ‘threatening packages’ that an obsessed fan has been sending Britney Spears

Entertainmentwise reported at the weekend how the singer has been forced to call in the FBI after receiving a string of suspicious mail.

Now a source who has seen the packages reveals to OK!: "It started about six weeks ago with just letters being sent once a week.

“And then it quickly escalated to larger packages that now arrive two to three times a week - always to the same L.A. address, but never to one of Britney's homes."

According to the insider, one of the items received was a sex toy, accompanied by two letters containing pornographic details of the writer’s fantasy sexual exploits with the star.

"The first thing you see when you open the box is a huge, lavender-colored, battery-operated sex toy. Still with the price tag on it,”  the source tells OK!.

It's claimed that the most disturbing item in the package was a a photograph of what may or may not be the sender - with his eyes cut out.

The man in the picture is described as "a middle-aged Caucasian male with stringy, greasy hair" and appears to be squirting some sort of yellowish liquid into his open mouth.

"It's like something from a bad movie," says the source. "If I hadn't seen it myself, I wouldn't believe it."