Four Frenchmen kidnapped in Niger three years ago have arrived back in Paris after being released.
President Francois Hollande welcomed them home at a military airfield.
The four were seized by al-Qaeda-linked gunmen in raids targeting French firms operating a uranium mine in September 2010. They were held in the northern desert of neighbouring Mali.
Their return comes amid reports that a ransom of 20m euros (£17m; $26m) was paid to ensure their release.
The French defence minister has said the four were freed without a military assault or a ransom being paid.
French Foreign Minister Laurent Fabius flew back with the hostages and told AFP news agency before take-off that the men were in "very good shape".
The BBC's Christian Fraser in Paris says that while the country celebrates the return of the four hostages, embarrassing questions are being asked of the French government over whether a ransom was paid for their release.
An unnamed source, quoted by Le Monde, said 20m euros was paid, from a secret fund operated by the intelligence services.
This echoes earlier comments from a member of the men's families that a ransom had been paid.
The government denies the claims.
Earlier this month, senior figures from French nuclear company Areva were in the Niger capital Niamey for a meeting with President Mahamadou Issoufou at which it is said certain guarantees were made.
Our correspondent says it seems unlikely that the French government would make a payment directly and that the focus is turning to what assurances or payments were made indirectly.
The group of four arrived back at Villacoublay military airfield, to the west of Paris, on Wednesday morning after a flight from Niamey.
The men - identified as Thierry Dol, Daniel Larribe, Pierre Legrand and Marc Feret - were seized on 16 September 2010 near Arlit. They were all employees at a uranium mine run by the French nuclear company Areva.
The al-Qaeda in the Islamic Maghreb (AQIM) group said it was responsible.
No further details of the men's release were given, but it is believed that Niger's top negotiator Mohamed Akotey, a former Tuareg rebel, secured the release over the last few days.
At least seven other French nationals are still being held hostage - two in Mali or Niger, one in Nigeria and four in Syria.