On July 31 2007, Greek authorities started investigating a Bulgarian claim that nine Byzantine-era plates on display at three Greek museums were smuggled out of Bulgaria.

The silver plates measure between 26cm and 33cm in diameter and are decorated with gold filigree. They date from the late 12th century, according to Greek experts.

The plates are currently on display at Thessaloniki’s Byzantine Heritage Museum, and Athens’ Benaki Museum and Byzantine and Christian Museum, according to the Associated Press (AP).

In the course of the investigation, prosecutors in Athens and Thessaloniki will interview Greek experts and museum officials.

The plates could be removed from the museums if evidence is found to support Bulgarian claims.

Earlier this month, Bulgarian prosecutor Kamen Mihov said he had “categorical proof” the artefacts were illegally excavated at a Bulgarian site.

Bulgarian prosecutors sent documents to Greece claiming the plates were excavated in late 2000 and 2001 at a site near the town of Pazardzhik in central Bulgaria.

The investigation into the Bulgarian claims was expected to last several months, according to judicial authorities. The results will be forwarded to Bulgarian authorities.