Highly dangerous pain-relieving drugs could be on the streets after being stolen from a pharmacy in the Spen Valley.

Police are warning people to be on their guard after more than 1,000 tablets - including morphine and the "date-rape drug" Rohypnol - were stolen during the break-in at a Heckmondwike chemist.

Police believe the thieves knew exactly which drugs they wanted and now fear they may end up in the hands of drug abusers.

The incident happened at 6.46pm on Sunday at the Co-op pharmacy unit in Northgate. A police spokesman said the intruders went to the back of the commercial premises in the town centre and forced the back door open, possibly using a jemmy.

The alarm was activated during the burglary but, once inside, the burglars attacked two locked and secure controlled drug cabinets and made off with the contents, without being seen by witnesses.

The drugs stolen included almost 500 morphine tablets, 500 temazepan tablets, 34 rohypnol (known as the "date-rape" drug) tablets, methadone, diamorphine and other pain-relieving drugs. Other drugs could also have been stolen, but until the shop does a stocktake, the exact quantities are not known.

Detective Sergeant Howard Atkin of Dewsbury police appealed for any witnesses to the incident to come forward.

"We are very concerned that these drugs may be coming into circulation in this area," he said, "We are asking members of the public to be aware of this and be on their guard.

"While these are prescription drugs, it doesn't make them in any way safe for people to use without proper medical advice. The reality is that people may use them for their side-effects rather than the purpose for which they are designed. This makes them highly dangerous.

"Whoever stole these knew exactly what they were looking for and targeted those specific cabinets."

Anyone who witnessed the incident, or believes they have been offered any of the drugs is asked to call Dewsbury police on (01924) 431059.