Police were called to a Bradford nightclub at the weekend after two men were left critically ill after collapsing unconscious outside the venue.

The men had been partying at the NV Nightclub in Great Horton Road before the 2.15am incident on Saturday.

Officers have now issued a warning about the potentially devastating consequences that illegal drugs or legal highs can cause.

It is not known whether the men, both aged 20 and not known to one another, took legal highs or illegal drugs before they passed out and it is also not known whether they took the substance inside or outside the club. But police issued the drug warning after the voluntary closure of the club, carried out in the early hours of Saturday with the agreement of the NV manager. They are now studying CCTV footage.

Chief Inspector Paul Hepworth, of Bradford South Neighbourhood Policing Team, said: “We do not know precisely what these men had taken during their night out on Friday, but it left both of them in a criticial condition.

“The potentially devastating consequences that illegal drugs or so called legal highs hold are clear and it goes without saying that using them on a night out is a huge risk.

“Hospital is not the place people want to be, particularly at Christmas and I would ask people to seriously consider their actions.

“We would always advise against ingesting anything into your body which is not for a bone fide medical reason.

“There are a number of substances, some legal and some illegal which people associate with drinking and partying. Even though some substances are legal it does not mean that they are safe to take, even more so when consumed with alcohol.

“This unfortunate incident is a classic example of highlighting the fact that any substance has the potential to seriously affect the health of the user and this should go out as a warning to all those who are intent on taking substances this festive season.”

Operation Northdale has just started which involves officers, Street Angels and Special Constables advising clubbers and partygoers about drug risks.

Both men were released from hospital on Saturday after making a full recovery.

Club manager Martin Dibb said they were stepping up searches throughout the Christmas period.