RAWLINS, Wyo. (AP) — Two Wyoming women have pleaded not guilty to charges of conspiring to bring a controlled substance into the state penitentiary.

Cheyenne resident Natalie Anderson, 30, and Katrina Pearson, 35, of Mills, are accused of trying to deliver the synthetic form of marijuana known as "spice" into the Wyoming State Penitentiary. They both pleaded not guilty on Monday.

Court documents say the women sent drugs into the prison through envelopes carrying magazine subscription cards that had been dipped in a liquefied form of spice.

A prison staff member became suspicious and began swapping out the tainted cards for clean ones and completed the delivery of the mail.

Authorities say the suspects were tied to the crime through phone calls from inmates and text messages.