Twelve old master paintings worth an estimated €4 million ($5.5 million) have been returned to the Museo Nazionale San Matteo di Pisa (National Museum of San Matteo, Pisa), according to the AGI. The works were missing from the museum for over ten years. Yet, for most of the time, no one even knew to look for them.

Dario Matteoni, the museum’s new director, spearheaded an investigation into the museum’s inventory last year. The museum then discovered that 12 paintings, which had been sent to a restorer in the city of Lucca in 2002 never returned. That restorer is reported to have been paid approximately €31,000 for his work on a total of 17 canvases for the museum.

Matteoni filed a lawsuit last December, demanding the paintings’ return. That suit lead to an investigation by the cultural heritage department of Italy’s national police force, which began in January 2014. They have since recovered ten of the works. The restorer had sold six of the paintings on to foreign dealers from whom they were confiscated.

The restorer, himself, turned over the remaining four canvases. Due to Italy’s 10 year statute of limitations on stolen property, he cannot be criminally prosecuted for keeping the paintings.