Khat, a plant that contains an illegal stimulant, is similar to cocaine but less intense. (The Associated Press)

Ten people were arrested in Northern Virginia, two in Maryland, four in New York and two in Ohio, according to documents filed in U.S. District Court in Alexandria. The alleged ring leader, Yonis Muhudin Ishak, is a naturalized U.S. citizen from Somalia living in Arlington.

Ishak used human couriers to transport khat into the U.S. from England, Canada, and Holland, officials said.

Authorities alleged that the conspirators sent packages of khat to this country using the U.S. Postal Service and private delivery companies. The khat was then distributed by mail and courier in at least 15 states, including California, Washington, Tennessee, New York, and the D.C. area, officials said.

Members of the organization then sent proceeds from their drug sales to others in England, Kenya, Somalia and Uganda, according to court documents.

Khat leaves contain the drug cathinone, an addictive stimulant that is similar but less intense than cocaine or methamphetamine.

Because the cathinone in khat leaves degrades over time, Ishak placed priority on ensuring the khat smuggled into the U.S. was fresh, officials said.

He would pay his 14 couriers about $1,000 a trip to travel to England and return with khat smuggled in their luggage, according to the documents. Ishak and others would rent cars for the couriers, and designate drop-off and pick-up locations for them.

At times, Ishak suggested his couriers use their children to carry the as a cover, prosecutors said in court papers.

All of those arrested were charged with conspiring to distribute cathinone, which carries a maximum penalty of 20 years. Officials said the investigation is still ongoing.