New York law enforcement officials have announced a crackdown on synthetic marijuana use, saying it has become a health crisis of near epidemic proportions nationwide.

At a news conference Wednesday, officials announced the unsealing of an indictment against 10 manufacturers and distributors in a massive distribution ring in all five boroughs.

U.S. Attorney Preet Bharara said the use of synthetic cannabinoids is causing deaths and sending thousands of people to emergency rooms around the country for treatment.

New York Police Department Commissioner William Bratton said the synthetic marijuana or "K2" was flooding the streets, harming teenagers in public housing and the homeless in city shelters in particular.

Six defendants were arrested Tuesday. Four are fugitives.