Results from forensic samples taken from the victims who mysteriously died at a South African nightclub last month have officially confirmed that all the teens who were found dead had methanol in their blood.

The 21 teenagers were found dead while slumped and lying on tables on June 26 at the Enyobeni Tavern in the city of East London, with no indication of how they could have died at the time.

“Methanol has been detected in all the 21 individuals that were there, however, there is still progressive analysis of the quantitative levels of methanol and whether it could have been the final cause of death,” Dr. Litha Matiwane, Eastern Cape provincial deputy director for clinical service, revealed in a press conference on Tuesday.

Methanol is the simplest form of alcohol in a chemical form and is not meant to be ingested by humans for recreational use. It is used for industrial purposes, such as for cleaning solvents, pesticides or alternative sources of fuel.

The teens, who all ranged in age from 13-17, were reportedly celebrating the end of school exams at the club. It is still unclear how they wound up ingesting the methanol, and police are waiting for more in-depth toxicology reports before a final conclusion is reached regarding the cause of death.

Matiwane did confirm that both alcohol poisoning and carbon monoxide inhalation were ruled out as potential reasons for the deaths, though traces of both were also detected in the bodies of all 21 victims.

The case caught the attention of the world and led to investigations and arrests of some club employees for selling alcohol to underage children.