Investigators are uncertain of the extent of damage at the Ahmed Baba Institute. But they fear many priceless documents have been destroyed.
The institute is one of several libraries in Timbuktu. It contains about 30,000 manuscripts, many of them collected from private family libraries throughout the country. Some of the fragile documents are bound by camel hide.
Some of the documents date back to the 13th century, a time when Timbuktu was a trading hub and center of Islamic scholarship. Some of the manuscripts, which cover topics ranging from history to politics, had not been catalogued.
The institute opened a new building in 2009, with the help of funding from South Africa.
UNESCO, the U.N. cultural agency, lists Timbuktu as a World Heritage site for its ancient mosques and shrines.
Islamist group Ansar Dine destroyed a number of ancient mausoleums in Timbuktu during the months they ruled the city.