Ricin was found in a London flat in January
Traces of the poison ricin have
been found at a railway station in Paris, according to the French interior ministry.
Two vials of the potentially deadly substance were found inside a locker at the Gare de Lyon, according to ministry officials.
Ricin, a toxin found in castor beans, can be fatal when inhaled or ingested.
The substance is 6,000 times more powerful than cyanide and has been used in the past as a bio-weapon.
In January, police in the UK discovered a stash of ricin during a raid on a flat in London.
Three men were charged with plotting
to produce chemical weapons in relation to the incident.
The Paris discovery was made on Monday by French police, after they received a telephone call from the state railway company SNCF, according to the French news agency AFP.
The locker contained "two vials with a powder, a bottle filled with a liquid and two smaller bottles also containing a liquid", said the ministry in a statement.
The two smaller bottles contained "traces of ricin in a mix that turned out to be a very toxic poison," the ministry added.
The announcement of the find came as the French authorities heightened security against terrorist targets following the launch of a US-led military strike against Iraq.
France has already doubled the number of soldiers in its streets, and ordered increased surveillance of train stations, ports and other sensitive areas.
Ricin is on America's Center for Disease Control and Prevention's B list of bio-warfare agents, and is therefore classed as a moderate threat.
The poison first came to the attention of bio-warfare experts in 1978, when Bulgarian dissident Georgi Markov was killed by secret agents in London who used a ricin-laced pellet fired from the tip of an umbrella.