A club-goer is in a coma, after falling ill at the Warehouse Project in Trafford.
The 32-year-old woman was hospitalised last night, after being seen by the nightclub's doctor.
She is thought to have taken a small amount of drugs. Last weekend, a man died after taking a substance at the same venue.
Medics placed her in an induced coma. Her condition is listed as critical.
Police arrested a 32-year-old man on suspicion of supplying and possessing drugs.
Charity worker Nick Bonnie died after taking an unknown substance at the club a week ago. Fifteen other people ended up in hospital.
The Home Office is now working with the venue on a drug-testing programme, in an attempt to keep clubbers safe.
The on-site doctor, who treated the woman taken ill last night, is also a new addition.
More top news
Two men from Stockport are facing trial in Abu Dhabi after being arrested in the United Arab Emirates.
Under-fire Manchester City boss Manuel Pellegrini wants to be judged at the end of the season.
The Speakers for Schools campaign launches in Manchester, getting young people involved in politics by discussing the topic 'Why I Vote'.