A woman has been injured after an explosion at the International Monetary Fund (IMF) offices in Paris.
French media reported that the person had opened a parcel addressed to a senior IMF official that contained an explosive substance, burning her hands and face.
A spokesperson for the Paris prefecture of police said: "An operation is underway for a person injured by a suspicious package with, according to preliminary information, a firework inside."
Investigators told BFMTV the device was a "large black cylinder, about 30cm long", with the blast so large the room's ceiling was hit by shrapnel.
Police authorities in Paris said the explosive substance was not a bomb but rather a homemade "big firecracker".
France’s anti-terrorism branch has opened an investigation into attempted murder, destruction through explosive means, possession of explosive substance and links with a terrorist initiative, French media reports.
A spokesman for the police said the IMF office had received threatening phone calls in recent days but there was no evidence that they were linked to the incident.
President Francois Hollande, who is on a visit to the south of France near Toulon, called the incident "an attack" and said those responsible will be found.
IMF director Christine Lagarde, who is on a trip to Germany, said in a statement she was informed about the explosion.
"I condemn this cowardly act of violence and reaffirm the IMF's resolve to continue our work in line with our mandate," she said.
Around 150 employees were evacuated from the building, in the 16th arrondissement, as a precaution and forensic officers were on site.
It came a day after a Greek anarchist group claimed responsibility for an explosive package found at the offices of Germany's finance minister, Wolfgang Schäuble.
"The package contained an explosive mix," Berlin Police said in a statement. "It was designed to cause severe injuries when the package is opened."
Investigators said the substance found was frequently used in the production of fireworks.
Greece's interior ministry said the package had a Greek stamp and was falsely put under the name of a New Democracy party member.
An investigation is underway into how the explosives bypassed Greek security checks to leave the country.
A spokesperson for Berlin Police could not confirm whether the incidents were linked.
A left-wing extremist group called Synomosia Pyrinon Tis Fotias (Conspiracy of Fire Nuclei) has claimed responsibility for the package in Germany, Bild reported.
After a series of firebombings, several members were arrested in 2009 and 2010 while attempting to send parcel bombs to embassies, EU leaders and organisations.
