ZIONSVILLE, Ind. -- A woman who reported being attacked and raped in a Boone County barn in March lied about the case, sheriff's department investigators now believe.

The department said Wednesday that it has officially closed the criminal investigation into the case after determining the alleged victim – a 41-year-old woman – lied to police. Investigators further found evidence at the crime scene that contradicted her statements.

The woman, who has never been identified, has stopped cooperating with the investigation altogether, the department said.

The woman told police in March that she was taking 76-year-old Helen Fix – for whom she was a caregiver – on a walk when she was approached by a masked man with a gun near a barn on the property. She said the man assaulted her outside the barn and then forced her into the building, where he sexually assaulted her.

She was found naked and unconscious inside the barn. Investigators at the time said she was strangled with a rope and beaten over the head.

The woman was transported to the hospital in critical condition. Fix was not injured during in the incident.

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The Boone County Sheriff's Department said the woman was injured, but that the rest of her story does not now appear to be true.

Sheriff Mike Nielsen released the following statement Wednesday saying the department still doesn't know why the woman would file a false report of this nature:

"As far as a reason for this reported incident, we can only speculate on the participant's motive. Our criminal investigations division has worked many hours on this case. As I have stated in prior press releases, we take every case seriously and we will leave no stone unturned. In this case our investigators did not leave a stone unturned and the outcome proved in many ways that this crime did not occur. Although we can theorize why someone would do this, we cannot prove the reason why this crime was alleged by the participant because they have stopped communicating with us."

Deputy Ken Conley told RTV6 the department is still looking at the possibility of filing false reporting charges against the woman due to the large amount of resources dedicated to the investigation.

"We worked on this from the moment we had our team on the ground at this location, following up with many interviews… but right now, that preliminary investigation has been closed," Conley said.

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