DRUG workers last night issued an urgent warning after tests revealed batches of cannabis and legal highs circulating in a North-East town have been contaminated with potentially deadly crystal meth.

A drug treatment service in Darlington raised the alarm after a number of its users tested positive for the substance, a highly addictive Class A drug linked to psychosis, brain damage, strokes and death.

Those tested believed they had only taken cannabis or legal highs, and drug workers fear the contamination is a deliberate attempt to introduce crystal meth to the area.

David Gardiner, children and young people’s manager at Darlington Borough Council’s Drug and Alcohol Action Team, said last night: “There has been a small but significant number of incidents where tests showed that people who believed they had only used cannabis had other drugs in their systems.

“This has been followed by a number of people testing positive for methamphetamine (crystal meth) after taking legal highs.”

It is believed that batches of legal drugs with the street names of Jolly Green Granules, Bubble and Blue Balls may have been contaminated.

The Drug and Alcohol Action Team is now attempting to establish the scope of the problem, which it describes as completely new to the area.

Mr Gardiner said: “It is speculation at the moment, but all those tested said they had sourced the substances locally.

It looks like the problem could be linked to a local dealer.

“This suggests that the drugs may have been cut in a deliberate attempt to introduce the drug to the area.”

The drugs users who tested positive for crystal meth were unaware they had taken it.

Mr Gardiner said: “The most worrying fact is that it was a genuine surprise to those people that there was something else there.

“This suggests the contamination was not immediately apparent and proves that when you are buying illegal drugs, you can never know exactly what you are getting.”

Use of crystal meth is widespread in the US and Australia, but is now on the increase in England. Users can face up to seven years in jail and an unlimited fine, while dealers can be jailed for life.

The United Nations Office on Drugs and Crime estimates there are more than 24 million users worldwide.

The Drug and Alcohol Action Team is working with police and is reassuring the public that the presence of crystal meth is unusual for the area.

Anyone who believes they may have been affected by the contaminated drugs should contact their GP if they feel unwell. For confidential drugs advice, call drugs charity Frank on 0800-776600.