U.S. federal officials say they have busted an international drug trafficking ring that was responsible for smuggling tons of narcotics from the Horn of Africa to the United States.

The officials say law enforcement authorities across the U.S. simultaneously arrested 31 members of the drug ring Wednesday. They say another 13 suspects are being sought.

The group allegedly had smuggled 25 tons of a narcotic known as khat, valued at $10 million, into the U.S. Khat is a plant grown in Kenya and Ethiopia. It contains ingredients that are considered controlled substances in America.

Officials say the indictment announced today represents the largest khat-trafficking prosecution in U.S. history.

During the 18-month investigation, U.S. authorities seized more than five tons of khat, valued at $2 million, destined for sale in the United States.

Experts say khat-users chew the plant and experience euphoria, but the drug has many side effects including cancer, violent outbursts and stomach disorders.