In 1967, a mound at San Pablo, Morelos, was partially excavated for salvage reasons. The mound had at one time contained an estimated 150-250 burials, all associated with ceramics identical to certain vessels found at Tlatilco. In addition to being one of the earliest known mounds in central Mexico, the site is believed to be a burial mound, rare at any time period in Mesoamerica. Analysis of the burial ceramics in comparison to assemblages from other Middle Preclassic sites suggests that Tlatilco and other sites of its type are not one-period sites, but exhibit at least two phases, the earlier phase related to highland Olmec, the later to a localization of styles. The San Pablo Pantheon mound appears to represent only the later phase.