Military police are investigating claims that British soldiers may have been involved in heroin trafficking in Afghanistan.
Officials said they were aware of “unsubstantiated” claims that troops were buying the illegal drug from dealers and using military aircraft to ship it out the country.
An inquiry has been launched focusing on British and Canadian service personnel at airports in Camp Bastion and Kandahar.
Meanwhile security has been tightened, with additional sniffer dogs being used as part of the crackdown at the bases.
Afghanistan is the source of 90% of the world’s opium.
Some drug bosses in the war-ravaged country have implicated soldiers in the trade.