Three people are seriously ill in hospital after apparently taking a new and relatively unknown drug bought at an illegal rave.
The men, one aged 19 from Brighton, were taken ill after a rave at the Omnipak factory in Biggleswade, Beds, in the early hours of Sunday.
It is believed they took a new drug in tablet form known as either DO9 or DOI.
Police said the drugs could have been bought at the rave in Biggleswade or at a separate event near Milton Keynes.
That event had been broken up by Thames Valley Police earlier and many of the rave-goers then travelled to Biggleswade.
Police are warning anyone who bought the drug not to take it.
They are advising anyone who has taken it to seek medical help.