The library at the University of Michigan was briefly closed last month after staff discovered venomous spiders in a storage facility. 

The three Mediterranean recluse spiders were found late last month in the Shapiro Undergraduate Library, The Associated Press reported, and the building was treated this week for spiders. 

The school told the outlet the arachnids did not enter any public spaces and the facility was only closed on Sunday and Monday as a precautionary measure.

"We apologize for the inconvenience to the university community," a spokesperson for the school said. 

Mediterranean recluse spiders have a poisonous bite and gravitate toward dark areas like caves and boiler rooms. They have been found around the world. 

“You’re really unlikely to be in any kind of danger unless you have to be in close contact,” professor Anne Danielson-Francois said according to the Detroit Free Press. “But if you’re the plumber crawling through a crawl space that has a lot of these spiders, then you could be bit, and that would be concerning. But just walking around the library stacks, it’s a very, very low risk.”

Mediterranean recluse spiders have been found in more than a dozen U.S. states in recent years, according to multiple reports.