The Eighth Circuit, in a pair of decisions addressing Missouri convictions for possession of a controlled substance and possession of a controlled substance with intent to deliver, has determined that Missouri's drug statutes are divisible and that the identity of the drug is an element of these statutes. As such, the modified categorical approach can be employed to determine the identity of the substance.
The decision in Bueno-Muela v. Sessions can be found here:
http://media.ca8.uscourts.gov/opndir/18/06/171267P.pdf
The decision in Lemus Martinez v. Sessions can be found here: