Anthony's attorney didn't immediately respond to a phone and e-mail message for comment.
Investigators have been searching for 3-year-old Caylee Anthony since mid-July when she was reported missing after not being seen for about a month.
Prosecutors had extended an offer of limited immunity to the mother in exchange for cooperation.
Investigators have called Casey Anthony a person of interest in Caylee's disappearance. She faces charges of child neglect, obstruction and making false statements in the case.
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