The clubbers, aged 20 and 21, died within hours of each other at the same hospital after attending separate dance music events at Alexandra Palace in north London over the weekend. Another 20-year-old man, also thought to have attended an event at the venue, is also being treated at the same hospital where he is said to be in a serious but stable condition. Last night Scotland Yard issued a special appeal to any young people who may have taken drugs at or before either of the events to seek immediate medical attention amid fears dealers may have been peddling an ultra-strong batch. It comes just a week after the charity Drugscope, which monitors trends in underground the drug trade, warned of an alarming rise in the popularity of ecstasy which dominated the 1990s rave scene but fell out of fashion. A surge in use follows an influx of a more-potent Chinese variants of the drug which is based on the chemical MDMA, or methylenedioxymethamphetamine.