French health authorities are racing to contain scattered cases of the more contagious delta virus variant, as France prepares to reopen its borders to vaccinated visitors and celebrates plunging COVID-19 infection and hospitalization rates.

Health Minister Olivier Veran said Sunday that France has multiple clusters of the variant, first identified in India and believed to be fueling a rise in infections in neighboring Britain, notably in the southwest Landes region. Speaking on BFM television, Veran said the variant hadn’t spread widely into the community and that health investigators are working to track cases.

Overall, he insisted, “the epidemic situation continues to strongly improve around the country,” but said the government isn’t preparing to lift mask requirements anytime soon. With growing numbers of people packing into Paris’ sidewalk cafes, parks and riverside quays, Veran warned that it’s too early for people to let down their guard, notably until more are fully vaccinated.

The French public health agency’s latest weekly epidemiological report shows a sustained drop in virus infections, hospitalization rates and deaths even after France started reopening schools, stores, and restaurants last month. More than half the adult population has had at least one vaccine dose, and 23% are fully vaccinated.

Emboldened by signs the virus is receding, one of the world’s most-visited countries is reopening borders to vaccinated travelers from the U.S. and much of the world starting Wednesday.

The delta variant is now dominant in Britain, and its spread has prompted France and some other countries to impose new restrictions on visitors from the U.K.. Britain’s public health agency said early evidence suggests there may be an increased risk of hospital admission from the delta variant.

The French health agency reported cases of the delta variant in multiple French regions, most linked to people arriving from India. While case numbers remain low, the agency said, “the multiplication of episodes … augments the risk of local transmission of this variant.”

France has registered more virus cases than any country in Europe and among the world’s highest virus-related death tolls, at more than 109,000 lives lost.