British military police are investigating claims that the country's servicemen may have trafficked heroin out of Afghanistan, the Ministry of Defence in London said Sunday.
An inquiry has been launched into what officials termed "unsubstantiated" allegations that service personnel had bought the drug and used military aircraft to transport it out of the war-torn country.
British troops at airports in Camp Bastion and Kandahar are under investigation and security has been tightened with additional sniffer dogs brought in as part of the crackdown.
"We are aware of these allegations," said a ministry spokeswoman.
"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."
She added that if any British troops were found to have smuggled illegal narcotics they would "feel the full weight of the law".
Afghanistan is the world's largest heroin producer with annual exports worth up to three billion dollars helping fuel a nearly nine-year Taliban insurgency.