Kamofie & Co. reported the necklace stolen on Jan. 22, roughly three weeks after Lohan was released from three months of court-ordered rehab at the Betty Ford Center.
Police obtained a search warrant Tuesday to try to retrieve the necklace from Lohan's house, but the item was turned in to detectives before the warrant could be executed.
Attorney Shawn Chapman Holley insists Lohan did nothing wrong and they will fight any charges if they're brought to court.
A celebrity website has reported that Lohan will be charged with grand theft as early as Monday.
However, the district attorney's office denied that any charges are pending, saying the case is still under investigation.
If she is charged, the case would be the latest problem for the actress, who has struggled to comply with the terms of her probation for a 2007 drunken driving case.
Judges sent her to jail last year twice for violating her probation, and a judge has threatened to sentence her to up to six months in jail if she cannot stay out of trouble.
On top of it all, prosecutors in Riverside County were also considering pressing battery charges against the troubled actress for a December altercation with a rehab worker at the Betty Ford Center.
The "Mean Girls" star was due in court on Feb. 25 for a probation status hearing.