France's agriculture ministry said Thursday that it was increasing surveillance of fields to stave off a ruinous virus affecting tomatoes that has already been found in neighbouring countries.

No French cases have yet been reported of the "tomato brown rugose fruit ," known as ToBRFV, which causes the fruit to develop rough discoloured patches on the skin that make it unmarketable.

There is no known treatment, and once the disease is found farmers usually have to destroy entire fields or greenhouses of the plants.

"The ministry's food health division is taking this risk very seriously," the ministry said in a statement.

The virus is reportedly a risk for peppers and other plants as well, but has no impact on humans.

The first cases were reported in 2014 at greenhouses in Israel and the next year in Jordan.

Growers in Spain and Italy—the EU's biggest tomato producers—have since been affected, as have some in the US and Mexico, and Britain announced its first cases last July.

Germany managed to eradicate an outbreak in several greenhouses by ripping out the and destroying them, and then treating the soil with disinfectants.

"Official surveillance is being carried out across French territory, in particular in greenhouses in vegetable producing regions," the ministry said.

It added that at least 350 inspections of tomato, pepper and eggplant fields would be carried out this year, on top of regular testings of crops, even those not showing symptoms.

Seed and seedling imports from countries where the virus has been reported will also be systematically checked, it said.