Residue extracted from the inner surface of one of three cylinder jars produced a mass spectrometer reading confirming that it contained theobromine (Crown and Hurst 2009: 2011).
Crown, Patricia L. and W. Jeffrey Hurst 2009 Evidence of Cacao Use in the Prehispanic American Southwest. Proceedings of the National Academy of Sciences, USA 106(7):2110-2113.