The human bodies appear to have been disinterred between 1870 and 1958. During that time, a local tax was in place requiring a fee to be paid for "perpetual" burial. Some bodies for which the tax was not paid were disinterred, and some—apparently those in the best condition—were stored in a nearby building. The climate of Guanajuato provides an environment which can lead to a type of natural mummification, although scientific studies later revealed that some bodies had been at least partially embalmed.