At least seven persons died and five were in coma after allegedly consuming drugs at an electronic dance music festival in Vietnam’s Capital city Hanoi on Sunday, reported AFP. The deceased were in their 20s while the five people in a coma are between 18 and 30 years old, said officials.

“Police investigators are trying to figure out what type of drug that was,” Hanoi Police Deputy Director Nguyen Van Vien said on Monday as authorities banned all EDM festivals in Hanoi. Investigators are also trying to find out who brought the drugs to the venue.

If the fatalities are confirmed as drug-related, it could be one of the worst mass deaths at a music festival on account of narcotics usage.

The deaths took place at the “Trip To The Moon” festival hosted by Vietnam Electronic Weekend at an upscale locality known for its nightlife and popular among expatriates, teachers, and youth. DJ Yellow Claw and Headhunterz were a part of the line-up, and the festival was attended by hundreds of people.

“The incident yesterday... was very painful,” said Tran Xuan Ha, deputy head of Hanoi Government’s Propaganda Department. “It was a great loss.”

According to official figures, there are close to 2,20,000 registered drug users in Vietnam. Vietnam’s porous borders from the notorious “Golden Triangle” drug-producing zone, comprising Laos, Myanmar, and Thailand, are responsible for the inflow of most synthetic drugs.