French health authorities on Thursday announced the death of a teenage girl who had contracted swine flu but also suffered from another serious illness complicated by a severe lung infection.
It was the first death in France of a patient suffering from A(H1N1), but the national health monitoring agency cautioned that the tests showed the 14-year-old's death was not "directly linked to the virus."
"This young girl suffered from a serious illness, complicated by a severe pulmonary infection," said a statement from the InVS institute.
The teenager had tested positive for the virus earlier this year and died more than a week ago in hospital in the northern city of Brest.
If confirmed as a swine flu death, France would join Belgium, Britain, Spain and Hungary as European countries with fatalities linked to the virus.
France has registered 1,022 cases of swine flu, far fewer than in Britain, Europe's hardest hit country, where some 110,000 people have been infected by the virus that first surfaced in Mexico in April.
A total of 31 people have died in Britain and health officials there said they believe the pandemic may be levelling off.
More than 800 people have been killed around the globe by the A(H1N1) virus and the World Health Organisation has warned the pandemic is now unstoppable.
France's Health Minister Roselyne Bachelot predicted that the virus will gain ground in the fall when children go back to school.
"It is absolutely certain that the new school year -- with children back at school, a change in lifestyle, warm weather followed by colder temperatures in the winter -- will help the virus spread," Bachelot told France 2 television.
"We must prepare ourselves, which is what we are doing now," she added.
France will probably raise its swine flu alert from a level five to six in September, the health minister said earlier this week.
That would trigger a catalogue of measures including the possible closure of schools to combat the pandemic.