Crack cocaine is taking over from heroin as the biggest selling hard drug in Bradford, police revealed today.

The worrying rise in the use of the highly-addictive drug, pictured, is being fuelled by an upsurge in trafficking by illegal immigrants from Jamaica, often known as Yardies.

And to cash in on the growing demand, established local dealers are now touting crack alongside their traditional mainstay trade of heroin.

Produced by purifying powdered cocaine into raisin-sized rocks selling at £20 each, crack induces an intense high but, unlike heroin, only lasts for a few minutes.

Detective Inspector Sheridan Moore, head of Bradford North police's drug team, said: "Once this has passed, the addict wants another rock and then another. Many will not think twice about spending £100 in a day. It is highly addictive from an early stage."

And most of the city's addicts will turn to robbing, burgling, prostitution or dealing themselves to fund their habits.

During the mid-eighties, when Bradford became regarded as the 'heroin capital of the North', cocaine and crack were rare in the city.

But by the early nineties, police noted both were becoming increasingly prevalent and they have witnessed a steady growth ever since.

"Certainly one factor in its increased use is its availability," said Det Insp Moore.

"There is now a lot of crack cocaine coming in from the West Indies and South America."

He said: "This can be linked to illegal immigrants, particularly from Jamaica, coming in to the area. They have contacts back in that country who use them as a distribution point here."

Yardie involvement has been highlighted in recent police successes against dealers, particularly in the Manningham and Lidget Green areas.

"Since February, the Bradford North drugs team has arrested 26 illegal immigrants, all but one from Jamaica, as part of its operations against class A drug dealing."

Most travel from the Caribbean using normal return tickets, never intending to make the homeward journey.

"I would say that compared to heroin, sales of crack are around 50/50, if not edging ahead. I certainly wouldn't be surprised if it was more prevalent already," said Det Insp Moore.

Many crack addicts were already taking heroin when they were introduced to smoking crack. Most 'mix and match' with both, using crack as an 'upper' and heroin as a 'downer'.

Crack dealing is no longer restricted to Jamaicans, with local pushers cashing in on the lucrative market, Det Insp Moore added.

"Traditionally a lot of heroin dealers have been young Asian men but we are now finding they are dealing crack as well."

One dealer was arrested last month in Ingleby Road with 24 mixed wraps.

"In the past, the same dealer would have just sold heroin, there is no doubt about that," said Det Insp Moore.

Since April, the Bradford North drugs team has charged 21 suspected dealers - ten for heroin, six for crack and five for both.

"The problem we face is that they operate very covertly. Someone dealing on the street may only have one or two wraps on him with the rest hidden nearby."

During a recent bust in Lidget Green, officers discovered more than 60 bags of crack behind a loose rock in a stone wall.

Det Insp Moore said: "We are having successes against these people but we rely heavily on information from the public. Often, a snippet of information, such as a car registration, will support our own intelligence and prove a great help. People might not see us directly doing something immediately but any information is taken seriously and is always acted upon."

Bradford North drugs team can be contacted on (01274) 376059 and the confidential Crimestoppers line on 0800 555111.