The findings of an internal affairs investigation into allegations of wrongdoing by a former Slidell Police Department detective have been turned over to the state Attorney General’s Office and the 22nd Judicial District Attorney’s Office, according to the Police Department.

The Attorney General’s Office is reviewing the case against Mario Arthur III, according to a news release from the Police Department.

An internal audit of the department’s Criminal Investigations Division last June showed that Arthur had been grossly negligent in his duties and had mishandled evidence, Sgt. Daniel Seuzeneau said in the release.

Arthur was transferred to the Patrol Division while the audit continued, and authorities found multiple cases that had not been properly investigated, Seuzeneau said. They have since been reassigned to other detectives and properly handled, he said.

The internal affairs investigation sustained allegations against Arthur of neglect of duty, unsatisfactory performance and insubordination, Seuzeneau said.

Arthur resigned earlier this month.

“Our detectives are held to the highest level of standards,” Slidell Police Chief Randy Smith said in a statement. “This type of negligence is an isolated incident and is completely unacceptable. We want to be transparent with this investigation, which is why we asked an outside agency to review our findings.”

Slidell police declined further comment, citing the ongoing investigation by the state.

Smith will take office as St. Tammany Parish sheriff July 1.

Follow Sara Pagones on Twitter, @spagonesadvocat.