The director of the Metropolitan Museum of Art said he's "increasingly concerned" about security at historical sites in Egypt and is urging action on the part of Egyptian authorities that they be protected.

In a statement released on Thursday, Met Director Thomas Campbell said the reports "appear to refer to a regrettable incident that took place several weeks ago," adding that the arts community is concerned. The Met would not detail whether any items were missing from the expedition site.

Egypt's head of antiquities, Zahi Hawass, released a list on Monday that detailed the cultural items missing since the country's January revolution that forced President Hosni Mubarak from power. Hawass said several sites were broken into, including an archeological expedition by the Met in the city of Dahshur.

The New York Times reported Thursday that Hawass has decided to step down from his post.