UNRELEASED music and personal belongings were stolen from singer Amy Winehouse's home in the days after her death.

The star's father, Mitch Winehouse, believes one of her acquaintances took copies of unreleased tracks, lyric books and letters. And he has vowed to root out the culprits when he returns from a family holiday taken to come to terms with his loss, The Sun reports.

Around 20 people -- including family, friends, security and police -- had access to the home since Amy Winehouse died.

Other items the singer's management cannot account for include one of her favorite guitars and lyrics scribbled for her third album.

"This is such a sickening shock to the family," a friend of the singer told The Sun. "That someone would stoop so low. They can't get their heads around it."

"Mitch is livid," the friend added. "The family, record label and management are months away from deciding what to do with any unreleased music. For that to be taken out of their hands is horrible."

Winehouse's home in North London was declared a crime scene after her death in July.

Her father -- who later handed out items such as clothing to mourning fans outside Amy's home -- has been required to complete an inventory of valuables.

"Mitch is willing to give whoever has stolen the items a chance to do the right thing and put them back so it doesn't have to get messy," the source said.