A package of K2 containing herbs and spices sprayed with a synthetic compound chemically similar to THC, the psychoactive ingredient in marijuana. Synthetic marijuana has been sold under several brand names, including K2, Spice, Crazy Clown and Scooby Snax. (Kelley Mccall/AP)

At least seven people staying at the District’s largest homeless shelter overdosed on synthetic marijuana Friday, the D.C. fire department said.

Fire spokesman Timothy Wilson said that emergency medical personnel were evaluating several other people who seemed to have used the drug, and had sent a team to check out anyone else at the Community for Creative Nonviolence shelter who might need medical attention.

He said D.C. police were also canvassing the area.

Wilson said that the victims, who all seem to have used the same drug, appeared lethargic, unresponsive or incoherent after taking it. All of them were in serious condition but were expected to survive, he said.

Several of the victims were found lying on streets in the area of the 1,350-bed shelter, which is in the 400 block of Second Street NW, Wilson said.

Eric Sheptock, an advocate for the homeless in the District, said he saw one of the overdoses Friday. He was walking down Second Street and saw a person leaning on a pole — drunk, he thought.

He helped the person lie down and called 911. When paramedics arrived, they told him that they had seen several similar overdoses earlier in the day.

Sheptock spoke to homeless people in the area, who said they believed a powerful batch of synthetic marijuana had recently arrived in the District from New York.