Police were called to the Home Office after suspected Class A drugs were found in the department’s headquarters.
Scotland Yard confirmed a “small quantity” was found by security staff at the Marsham Street building in central London on 3 May.
Officers seized the drugs but added no further action was necessary and advice had been given to security.
The Home Office said it takes incidents of this nature “extremely seriously” and appropriate action had been taken.
Reports in the Sunday Mirror suggest the substance found was crystal meth, possession of which can result in a maximum sentence of seven years in prison.
A Home Office spokesman said: “A small quantity of drugs was found within the 2 Marsham Street estate. The incident was referred to the police by building security, who attended the site and removed the substance.
“The police advised no further action was needed.
“We take incidents of this nature extremely seriously, always ensure that proper procedures are followed and take appropriate action based on the advice of the police.”
The incident happened a few days after Sajid Javid replaced Amber Rudd as home secretary.
A Metropolitan Police spokesman said the drugs were found in “a communal area by security staff” and police attended at 17:00 BST on 3 May.
“The substance was seized by officers and taken to a local police station. Advice was provided to security staff. No suspects have been identified at this time.”
‘Class A drugs’ found at Home Office headquarters}