The South Dakota attorney general has closed its investigation into billionaire T. Denny Sanford for possession of child pornography and is not filing charges, according to a notice the office sent to a judge Friday.

The office “has completed its investigation” and “has determined that there are no prosecutable offenses within the jurisdiction of the State of South Dakota,” deputy attorney general Brent Kempema wrote.

The attorney general’s office provided no details on how that decision was made or whether Sanford is being investigated in any other jurisdictions or by federal authorities.

“Mr. Sanford appreciates the public acknowledgement by the SD Attorney General’s office” that the office’s Division of Criminal Investigation “has concluded its investigation and they have found no prosecutable crime,” one of Sanford’s attorneys, former South Dakota attorney general Marty Jackley, told ProPublica.

In 2020, ProPublica first reported that South Dakota authorities had started investigating the state’s richest man and had referred the matter to the U.S. Department of Justice.

Earlier this year, South Dakota officials acknowledged Sanford was still being actively investigated by federal and state authorities.

The Department of Justice declined to comment about whether its probe was still open.

The investigation of Sanford started with a tip from the National Center for Missing & Exploited Children, court records show. The center is a private nonprofit that operates a tip line where people and companies can report images of suspected child sex trafficking and abuse. The organization’s staff reviews the tips and refers them to law enforcement.

Investigators obtained five search warrants in 2019 and 2020 for Sanford’s email, phone and internet data. It’s unclear what, if anything, investigators found in the searches.

ProPublica won access to the search warrants after more than a year of litigation that reached the state’s highest court. Sanford unsuccessfully asked the courts to conceal the search warrants, which are supposed to be publicly accessible under state law, and to block ProPublica’s reporting.

ProPublica is continuing a legal effort to obtain other records filed with the court that detailed why there was cause for those warrants. Sanford is fighting to keep those records private.

Sanford’s attorney has previously said that Sanford’s email account was hacked and being used by someone else.

In a new filing Friday, another of Sanford’s lawyers said a forensic examination of Sanford’s email account “uncovered the specific name of an individual other than the Implicated Individual having gained access.”

“Further evidence includes corroborating evidence of hacking,” Sanford’s attorney wrote, without providing any details.