A man has died of a suspected drug overdose and three others were stabbed as thousands attended two illegal raves in Manchester on Saturday night.
The 20-year-old man had been at a large gathering of about 4,000 people in Droylsden, according to Greater Manchester Police.
There were reports of three separate stabbings at another rave in nearby Carrington involving about 2,000 people, police said.
An 18-year-old man suffered life-threatening injuries - and two other men, aged 25 and 26, were also injured.
A 25-year-old man was arrested on suspicion of possession of an offensive weapon, police said.