The criminal investigation into two missing pieces of artwork at the Boston Public Library's flagship branch in Copley Square is officially over, concluding a controversial chapter that led to the ouster of the library's top executive.
The Boston Police Department, which was leading the investigation with assistance from the FBI, quietly closed its involvement in the case June 4, said Boston police spokesman Lieutenant Michael McCarthy, who provided no further details about the investigation.
The missing prints — an Adam and Eve etching by Albrecht Dürer worth more than $600,000 and a Rembrandt self-portrait valued up to $30,000 — were eventually found unharmed and not far from where they were last seen.
"Because it has been determined that the art was misplaced, the BPD no longer is conducting a criminal investigation,'' McCarthy wrote in an initial e-mail response to a Globe inquiry.
David Leonard, the library's interim president, thanked authorities who assisted in the investigation, saying in a statement the library is making steady progress in its Print Department inventory.
"We have implemented additional security procedures to ensure the protection of our collections,'' Leonard said. "We're currently focused on moving the institution forward, and preparing for additional collection inventory work in the coming months."
The library staff discovered the Dürer missing April 8 and launched a search in locations where the print may have been misfiled, the Globe previously reported.
A week later, the staff discovered the Rembrandt self-portrait also was missing and notified Police Commissioner William B. Evans and Mayor Martin J. Walsh. A police report was filed April 29, and the Boston Police Anti-Corruption Unit launched an investigation.
Evans said at the time that authorities were looking at "the possibility of it being an inside job,'' raising the prospect that a library employee had stolen the works.
Library officials had said the library was working closely with police on the investigation and conducting an independent security review and an item-by-item audit of its print collection.
The missing artwork put the library under rare, intense scrutiny. A staff member was placed on paid administrative leave, concerns were raised about whether more artwork might be missing, and the library's president, Amy E. Ryan, resigned amid withering criticism from the public and from the mayor.
The two prints were discovered June 4 — the day after Ryan resigned — on a shelf, 80 feet from where they should have been filed. Library officials said the prints were misfiled.
Despite the discovery, Evans said at the time the criminal probe would go on.
"The anticorruption unit will continue trying to determine if anything else is missing," Evans said. "We will be examining what they have there. The investigation is not over."
The police closed the case that same day without notice to the public.