BLAINE, Minn. – After nearly a dozen teenagers overdosed and one died from taking a hallucinogen at a house party, investigators determined the substance was a version of a banned rave-party drug that can be purchased online.

Initially, authorities even said it was legal.

But the case of the concoction called 2C-E exposes a law enforcement gray area surrounding a dangerous class of “cousin drugs” that in some cases are only a molecule apart from their banned relatives.

Authorities on Friday arrested a 21-year-old man suspected of providing the drug to the teenagers. He was being held on suspicion of third-degree murder.

The dead youth was identified as Trevor Vance Robinson, 19, of Coon Rapids. He was one of 11 people ranging in age from 16 to 21 who fell ill late Wednesday in this Minneapolis suburb.

When the first officers arrived at a home in Blaine, they found a group of young people who were having trouble breathing, and some appeared to be hallucinating.

“They weren’t necessarily in the right time or place,” police Capt. Kerry Fenner said. “They probably weren’t in real time.”

By the time more officers arrived, most of the party-goers had either fled or been taken to hospitals. Many of them were found around the neighborhood, police said.

By Friday, most of the 10 survivors had been released from hospitals.

Andy Young, 18, a good friend of Robinson’s who said the two had done drugs together, described 2C-E as combining the effects of LSD and psychedelic mushrooms.

“You couldn’t really focus on anything. Your mind is racing,” Young said of his experience on 2C-E. “You don’t know what’s going on at all.”

Friends said Robinson had a son who is less than a year old.

On Friday, two women who arrived at the house where the party took place declined to answer questions from a reporter.

Michelle and Michael Fisher, the parents of the teenager who threw the party, had been out of town, and their son was supposed to be staying with a friend, said Greg Fisher, 61, of Maplewood, who said he was the boy’s great-uncle.

Sometimes known as “Europa,” 2C-E is not specifically listed as a “Schedule I” controlled substance, such as heroin, cocaine or LSD, the kind that is banned by name because it has no approved medical use.

The same is true for similar drugs available online called 2C-I and 2C-T-7. But a related substance known as 2C-B has gone through the slow and cumbersome process for a formal ban, and federal officials say that’s good enough because federal law allows prosecutions for “analogue” drugs.

“You may be able to purchase it on the Internet, but it ain’t legal,” Drug Enforcement Agency spokesman Rusty Payne said Friday.

Minnesota authorities who announced the overdoses Thursday clearly thought otherwise because 2C-E is not covered by the state’s drug laws, which they are more accustomed to enforcing.

Informed about the DEA’s position on the federal law Friday, Fenner said that might be one way to pursue prosecution.

“They’d be the experts on that. … Those are the people we rely on,” Fenner said.

When authorities announced Friday’s arrest, they cited the analogue law.

A prosecution would be welcomed by John Kennedy, who lives next door to the house where the party was held.

Kennedy said he doesn’t know the family well, but he described the boy believed to have hosted the party as a nice kid who likes to skateboard.

“Whoever got that stuff for those kids ought to be put in jail,” Kennedy said.

The various 2C drugs fall into a family known as phenethlyamines — hallucinogens with similar chemical structures. They have effects comparable to much better known “club drugs” such as Ecstasy.

“They’re all just a molecule away from each other,” said Carol Falkowski, a drug abuse strategy officer with the Minnesota Department of Human Services.

She said party drugs were more common here about 10 years ago, when raves were popular. This is the first time she’s heard of 2C-E use in Minnesota.

The drugs are often marketed on the Internet as “research chemicals” in an effort to skirt drug laws, and some suppliers claim they are not intended for human consumption.

“We are dedicated to maintaining our flawless legal integrity and will not sacrifice it for anything,” says one site offering such drugs.

“Any indication of intended misuse on the buyer’s behalf will result in the buyer being permanently banned from ordering,” the disclaimer says.

Payne said the DEA views 2C-E and other party drugs as an ongoing problem nationally.

“I don’t know if they’re growing,” he said. “We’ve had problems with designer drugs for years.”

But Caleb Banta Green, a research scientist with the Alcohol and Drug Abuse Institute at the University of Washington, said he believes party-drug use in general is on the rise in the Seattle area, even though figures are not available.

“We’re going to continue to see a lot of weird stuff,” Green said. “And it’s really dangerous.”

Green cautioned against getting “too hung up on one particular drug” because more keep emerging.

Lawmakers have struggled with similar challenges in their efforts to curb the trade in synthetic marijuana, often sold under the names K2 and Spice, as well as “bath salts” that contain an unregulated stimulant, MDPV.

The DEA recently banned five chemicals often used in synthetic marijuana, but replacements are available. The Florida Legislature and others are considering banning MDPV.

Jim Hall, director of Upfront Drug Information in Miami, said one attraction of such substances is that they often elude routine drug testing.

Would-be users need to realize that just because they get a designer drug, synthetic marijuana or “bath salts” from someone they know or over the Internet, it can’t be considered safe, even if it carries a label listing ingredients, Payne said.

They have no way to know what’s really in it, the conditions under which it was manufactured or the country of origin, he said. And there hasn’t been enough research on many of these substances.

“This stuff is dangerous and you’re playing Russian roulette when you put this stuff in your body,” Payne said. “Bad things are happening to people who abuse this stuff.”