Egypt’s minister of the interior told the official MENA news agency that a museum employee was most likely responsible for the theft of a valuable van Gogh painting from a museum in Giza last month, Agence France-Presse reported.

The painting, known as “Poppy Flowers” or “Vase and Flowers” and valued at more than $50 million, was cut from its frame on Aug. 21 at the Mohamed Mahmoud Khalil Museum, where it hung in a room with only some working cameras and no working alarms. Several Egyptian cultural officials, including Mohsen Shaalan, a deputy culture minister who heads the fine arts division of the ministry, have been charged with negligence.

Habib el-Adly, Egypt’s interior minister, said on Sunday that “many circumstances around the theft” indicated that “a museum employee participated in the theft or stole it himself,” citing the painting’s “location and placement” at the museum as evidence but without naming any suspects.

He added that “security services are continuing to take measures internally and externally through cooperation with Interpol and several other Arab and foreign security services” and that the theft of the van Gogh had been a “difficult lesson.”