Police are warning that a rogue batch of heroin may be circulating in Cardiff, following the death of one man who is believed to have taken the drug.

Three other people are seriously ill in hospital.

The man who died has not been named, but police have said he was 32 and came from the Roath area of the city.

The man died at the University Hospital of Wales

He died on arrival at the University Hospital of Wales after being taken in from the Canton area.

Another 24 year-old man is said to be in a life threatening condition after he was brought in to the hospital from the Llandaff North area.

A third man, aged 23, is said to be in a serious condition after he was admitted to hospital from the Cathays area.

The fourth person, a 27-year-old woman, is in a serious condition in Llandough Hospital near Cardiff.

She was brought in from the city centre on Friday.

Detectives are investigating the circumstances of the death of the Cardiff man and are trying to find the source of the heroin.

This death comes less than a fortnight after police in Bradford, West Yorkshire, issued a warning about tainted heroin in the town of Little Horton.

Crackdown

The rogue batch in Bradford is believed to have claimed four lives - including three people who died within eight days.

On 2 September, West Yorkshire Police urged drug dealers to dispose safely of any remaining substances and reminded drug users of the risks they were taking.

A similar killer batch was believed to have been circulating in Scotland last July when three men in Fife died suddenly.

The scare over tainted heroin comes as Welsh police launch a crackdown on drug-related crime.

At the end of August police in Gwent, South Wales and Dyfed Powys announced Operation Tarian - which means shield in Welsh - an initiative to stop gangs from Birmingham and Bristol flooding the market with cheap, hard drugs.

Police say heroin is rife in the south Wales Valleys

The three forces have said they will use armed police to combat drug-gangs whose members they describe as "violent criminals who target the young and vulnerable".

The police say that organised criminals - particularly Jamaican groups, the so-called Yardies - are already operating in a number of areas.

They rule by fear and their trademarks include drive-by shootings, public executions, and enslavement of prostitutes.

Police fear the gangs are seeking new heroin and cocaine markets in south Wales where the number of drug users registered by pharmacies has increased by 14% in the past six months.

Police say they have seized as much heroin in the past four months as they confiscated in the whole of 2000.

And in that year they seized double the amount of the previous year.

Promoting the new initiative, South Wales Assistant Chief Constable David Francis said that his message to the drugs gangs was:"You will not succeed with your gun culture in south Wales."