Some exhibits at the Smithsonian Institution have already been damaged and collectors are becoming unwilling to lend items for display because of deteriorating buildings and a lack of security, according to a report released Friday by the Government Accountability Office.

The world’s largest museum complex and its research organizations have been under increasing scrutiny after it was discovered this year the Smithsonian’s head had spent $90,000 in unauthorized expenses and charged the institution more than $1 million to use his mansion for official functions.