Updated

Three young people have been hospitalized with kidney failure and a dozen others sickened in Casper, Wyoming, in an outbreak linked to a batch of the designer drug Spice, authorities said on Friday.

State medical officials said the cause of the outbreak was under investigation but that Casper residents who sought medical treatment for vomiting and back pain had recently smoked or ingested a chemical-laced herbal product packaged as "blueberry spice."

The illnesses reported by physicians and hospitals in the Wyoming city beginning last Sunday added up to a cluster that alarmed health officials by the end of the week.

"At this point, we are viewing use of this drug as a potentially life-threatening situation," Tracy Murphy, Wyoming state epidemiologist, said in a statement.

Those who have fallen ill range in age from the late teens to early 20s and all used blueberry-flavored spice, said Bob Herrington, director of the Casper-Natrona County Health Department.

Harrington said the outbreak was causing concern among health and law enforcement officials in the city of 55,000 residents.

"Based on our information from the doctors, the three people with kidney failure are in pretty serious shape; they're very sick," he said.

Spice is sometimes sold as "legal marijuana" because of the high that users experience from plant material coated with chemicals that claim to mimic THC, the active ingredient in marijuana, according to the U.S. Drug Enforcement Administration.