A "minuscule" quantity of cannabis resin has been found at the Scottish home of Defence Secretary John Reid.
The discovery was made at Mr Reid's home several days ago.
Mr Reid said the cannabis - worth less than £1 - was found in a guest room and police had told him it could have been there for years.
"I have no idea where it came from, or when," the defence secretary said.
Police are to take no action over the find, made during a security sweep of the Lanarkshire house. They said Mr Reid was not suspected of any offence.
The property lies within his former constituency of Hamilton North and Bellshill.
In a statement, Mr Reid said: "There is absolutely no suggestion that this in any way involves me or members of my family and both I and the Strathclyde Police regard the matter as closed."
Assistant Chief Constable John Corrigan, of Strathclyde Police, said in a statement: "I can confirm that we have investigated the discovery of a small piece of cannabis resin in a guest room of a house within the force area.
"The substance found weighed less than one gram with a street value of approximately 85p."
The BBC's political correspondent Mark Saunders said the drugs were thought to have been found while Mr Reid was on an official visit to Afghanistan to visit British troops.
In his statement Mr Corrigan said the owner of the house "has co-operated fully with police and is not suspected of having committed any crime or offence".
He said it was a regular occurrence for Strathclyde Police to find or become aware of very small quantities of Class C controlled drugs that were not in someone's possession.
Sources close to the minister, who after boundary changes is now MP for Airdrie and Shotts, said the drugs could have been there for years, during which time "hundreds of people" had been through the house.
The accommodation was the Reid family home when his first wife, Cathy, was alive. She died in 1998 and the couple had two sons.
Mr Reid, 58, and one of Labour's biggest ministerial heavyweights, later married the film director Carine Adler.
He has previously served as health secretary, Northern Ireland secretary, Scottish secretary and leader of the house.