(AP) — Nine people have been indicted by a federal grand jury in Denver as part of a national crackdown on synthetic drugs.

Federal officials said Wednesday that the nine are from various states and some are also facing state charges. U.S. Attorney John Walsh says all are in custody after being arrested starting Wednesday morning.

Among those indicted is John Gilbert Bowen of Las Vegas. Investigators say he ran a business which sent synthetic drugs to Wisconsin, Nebraska, Alaska, Ohio, Georgia and Illinois as well Colorado.

Synthetic marijuana has been linked to outbreaks of illness in Colorado and elsewhere. It’s blamed for at least one death in Colorado — a 15-year-old Aurora boy who died last August.

While real marijuana is legal in Colorado, synthetic marijuana blends marketed under names such as K2 and Spice are not.