The Thriller-themed party was held in the Madrid Arena of the Casa de Campo. It is thought that a flare that someone released into the crowd caused the panic and the stampede. Video update November 5.
Sources at the Chief of Police in Madrid said that the flare was probably the trigger for the stampede and they are investigating, although at present no arrests have been made.
Emergency services received a warning about the 4.05 am that several young women, aged between 18 and 25, had been injured in the crush. Two of the girls died in the emergency medical infirmary in the premises, after more than 30 minutes of resuscitation attempts, a third died upon reaching the Clinico Hospital, where she had been taken, and another two are in a critical condition in the 12 October Hospital and the Jiménez Díaz Foundation.
The building was evacuated after the incident.
Tickets for the Halloween event.
An assistant at the party, who gave her name as Sandra, told Spain's Cadena Ser radio station that "There was a human crush at the only exit they had because the others were sealed off."
The building can hold 10,000 people and was packed for the Halloween celebration.
According to the website of Madrid Espacios y Congresos, the event was planned by the Diviertt company and offered, for 25 euros, a "Thriller Music Park" in a "fun and gloomy atmosphere achieved thanks to the visual and sound effects" with some well-known DJs.
The organization suggested costumes inspired by the video of Michael Jackson's Thriller, and announced as the star of the party Steve Auki, an electronic music artist, along with Julien Leik, Autoerotique, Army of the Universe and Ed is Dead.