BLAINE (AP) — 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 teens. 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.