A central Missouri man faces up to five years in federal prison now that he's admitted his role in a plot to smuggle into the U.S. chemicals used to make synthetic marijuana.

Thirty-year-old Wesley Upchurch of Columbia pleaded guilty Wednesday to a conspiracy count. A sentencing date was not immediately set.

Upchurch is the case's 18th defendant to plead guilty. Four of them already have been sentenced.

Upchurch admitted that he and other conspirators bought various synthetic cannabinoids in powder form from China over a three-year period to March 2014. The packages often had misleading labeling about their contents to avoid detection by law enforcers.

These chemicals were combined with other ingredients, such as generic potpourri, then packaged and sold at various retail outlets.

Spencer Platt, Getty Images