More illegal raves are planned in Greater Manchester this weekend, police have said.
Assistant Chief Constable Nick Bailey said they had "seen information that there are individuals who are planning to run unlicensed events".
He said "police intelligence cells" were gathering information to try to stop them happening and appealed to the public for help.
Footage seen by Sky News from one event, dubbed "The Quarantine Rave" by organisers, shows a huge crowd tightly packed in a small field.
"These events would be illegal at any time," said Greater Manchester Mayor Andy Burnham, "but they are particularly dangerous during a pandemic".
A man in his 20s died from a suspected drug overdose at one of the events, held in Oldham.
At the other event, in Carrington, police are investigating the rape of an 18-year old woman and several knife attacks.
Mr Burnham said: "There is no excuse for parents to be dropping off young people at these events, as we saw at the weekend.
"And to the young people, I understand how frustrating lockdown may have been for you, but if you go you are putting yourself at risk of serious harm, but also your family at risk of infection."
There have been reports of illegal raves being held across the UK, as pubs and clubs remain closed due to COVID-19 lockdown restrictions.
Greater Manchester Police promised "a stronger interventionist approach" to any future raves after the force was criticised for not intervening sooner during Saturday night's events.
Bev Hughes, deputy mayor for police and crime, said: "We will bear down with everything we've got to try and stop any repeat of this.
"The organisers, and attendees, of these raves are jeopardising the achievements of the previous 12 weeks of lockdown."