KENS-TV reports more than 200 dead bats, some just skeletons, were found inside the columns of the library during the examination.
State health officials, in a letter to library card holders and posted on the building's door, warned of potential risks for visitors.
A town hall meeting will be held Monday night at Pearsall city hall to discuss health concerns.
Pearsall is a city of about 7,900, located 50 miles southwest of San Antonio.