BBC News reports that Britain's Ministry of Defence is investigating reports that soldiers in Afghanistan have been using military aircraft to smuggle heroin out of the country.
The inquiry is focusing on British and Canadian service personnel at airports in Camp Bastion and Kandahar.
Security has been tightened, with additional sniffer dogs being used as part of the crackdown at the bases.
An MoD Spokeswoman said: "We are aware of these allegations. Although they are unsubstantiated, we take any such reports very seriously and we have already tightened our existing procedures both in Afghanistan and in the UK, including through increasing the use of trained sniffer dogs.