A 21-year-old man has died and two others have been taken to hospital after they fell ill at a nightclub.
The Metropolitan Police were called to The Cause in Tottenham shortly after 3am on Saturday morning after receiving reports that a number of people were unwell.
Detectives say the man's death is currently being treated as unexplained, and his next of kin have been informed.
A statement said: "At this early stage of the investigation it is understood that all parties have taken drugs.
"At this stage we don't believe any persons were known to each other."
No arrests have been made, and the two men in hospital are in a stable condition.
Superintendent Simon Crick said the incidents have caused "particular concern" - and he urged anyone who bought drugs in and around the nightclub to dispose of the substances as soon as possible.
He added: "An investigation is continuing to establish where these drugs have come from and I encourage anyone with information to contact police.
"If anyone has taken an illegal substance and becomes unwell then they should seek immediate medical advice."