A concertgoer died from an apparent drug overdose, a second is in critical condition and 20 others were transported to the hospital following a dance party at Merriweather Post Pavilion on Friday, Howard County police said.

Tyler Fox Viscardi, 20, of Raleigh, N.C., was transported to Howard County General Hospital shortly after 9 p.m., where he was pronounced dead, police said. Officials are still trying to determine what drug was in his system and may have to wait for an autopsy for confirmation.

A 17-year-old male from Woodbridge, Va., was transported to the hospital around 8:30 p.m., suffering from what appeared to be an overdose, police said. It does not appear the two young men knew each other, and police are also trying to determine what drug the teen took.

Police said at least 20 other people were taken to the hospital during the all-day Mad Decent Block Party. The event is a traveling music festival organized by the Los Angeles-based dance record label Mad Decent, which was founded by well-known DJ Diplo.

Police said many of those cases appear to be drug-related and that investigators are working to determine what drugs were involved.

A Howard County police spokeswoman wrote in an e-mail that it’s possible weather could have been a factor in people being sickened, since the event began in the middle of the afternoon.

“While we can’t confirm what role the weather may have played in anyone’s medical condition, we have seen cases of dehydration at various summer events in the past,” Sherry Llewellyn, the police spokeswoman, wrote.

Officers also issued 50 citations for underage drinking during the event and made three arrests, on charges including assault on a police officer, domestic assault and possession with intent to distribute marijuana.

Llewellyn wrote there have been reports of overdoses at other stops of the festival, but this was the first one that has been fatal.