A man who was at a student club night has died and a woman is seriously ill after taking what police said was MDMA.
The 19-year-old man fell ill at the drum and bass night at The Assembly in Leamington Spa, Warwickshire, at about 05:00 BST, and later died in hospital.
The 22-year-old woman remains seriously ill in hospital and police say others were also admitted after taking “Red Bull” pills.
Warwickshire Police urged people to check on friends who were at the night.
Officers said they did not know if the group had bought the drugs at the club.
Det Supt Pete Hill said they believed all those who were ill had taken the red pills containing MDMA, the active drug in ecstasy.
He added they were concerned others had also taken it and urged anyone who had to seek medical advice.
“If others were at the same event last night and are aware their friends took this drug, please check in on them,” Mr Hill said.
In a statement The Assembly, which is in Spencer Street, said: “We take the wellbeing of our customers extremely seriously, we continue to work closely with Warwickshire Police and reiterate our zero policy on drugs in our venue.”