A team of 26 French firefighters has been deployed to UK port city of Dover to help the UK "accelerate" the return of European citizens, French authorities said on Thursday. France also shipped out 10,000 coronavirus tests in a bid to tackle the backlog of trucks trapped at the port over fears about the spread of the new coronavirus variant.

French fire fighters and civil defense volunteers would help test truckers in Dover, French authorities said.

British and French authorities have agreed to keep the border between the countries open throughout Christmas, including rail and sea links, to help motorists and travelers return home. Additional staff members agreed to work during the holiday.

"Normally, we close on the 25th, but now, given the situation, the port will remain open," said Jean-Marc Puissesseau, president of the French ports of Calais and Boulogne-sur-Mer.

Thousands tested, three positive

The French government abruptly cut the flow of freight trucks from the UK on Sunday, asking for motorists to provide a negative coronavirus tests.

As a result, thousands of drivers have already spent several nights sleeping inside their vehicles close to the major cross-Channel port of Dover. Many of them are stranded on the nearby roads in the southeastern county of Kent or the old Manston airport which had been converted to a testing site.

The French ban comes after the labs in the UK detected an outbreak of a new and more transmittable coronavirus variant.

UK transport minister Grant Shapps confirmed the decision for borders to remain open: "We've agreed the UK/French border at Eurotunnel, Dover and Calais will remain open throughout Xmas in order to help hauliers & citizens return home as soon as possible," he tweeted, adding that of the 2,367 virus tests administered at the port as of Thursday afternoon, just three turned out positive.

Truckers likely to spend Christmas stranded

On Wednesday, UK officials said there were around 6,000 trucks waiting to cross the border. While some of them have since continued their journey, officials warned the backlogcould take days to clear and that many drivers will likely spend Christmas waiting inside their vehicles.

France's temporary shutdown of the border triggered concern across Europe as France acts as a major channel for trade and travel between the UK and mainland Europe. The UK relies on France for food at this time of year, especially fresh fruit and vegetables.