A French drugs squad officer has been arrested in the southern city of Perpignan on suspicion of stealing more than 50kg (110lb) of cocaine from Paris police headquarters.
The unnamed officer, 34, was picked up while on holiday in the city near the Spanish border, officials say.
The theft of the drugs, which have a street value of some 3m euros (£2.4m; $4m), was a major embarrassment.
It appears they were taken from a secure room on 24 July.
CCTV images of a man carrying two bags into police headquarters that night, and leaving shortly after, helped investigators identify the suspect, police say.
The drugs were originally seized in a raid on 4 July against a suspected Senegalese gang operating in northern Paris, Le Parisien newspaper reports.
There was no immediate indication on Saturday that the missing cocaine had been recovered.
Police headquarters, immortalised in Georges Simenon's Maigret detective novels and in French crime films, is located at 36 Quai des Orfevres, in the heart of the French capital, overlooking the River Seine and close to Notre Dame cathedral.
The building also attracted unwelcome publicity in April, when two elite anti-gang officers were charged with raping a Canadian tourist there. An investigation is still under way.