Efforts are continuing to try to track down Britons who have been missing since Japan's massive earthquake and tsunami one month ago.
The Foreign Office said there were no confirmed British fatalities but it was very concerned about "a small number".
Some 17,000 Britons are thought to have been in Japan when the quake struck, but hundreds fled in the aftermath as radiation leaked from a nuclear plant.
In all, UK charities have raised nearly £10m to help Japan and its people.
The devastating 9.0 magnitude quake and resulting tsunami on 11 March crippled the Fukushima Daiichi nuclear plant's cooling systems and caused some radiation to leak.
In its wake, a British team joined a huge search and rescue mission and found several bodies but no survivors.
Meanwhile, Britons living and working or on holiday in Japan boarded commercial flights for Hong Kong, and fled some of the worst-hit areas on coaches or UK government-chartered planes.
But not all Britons thought to be in the country have been accounted for - Japanese authorities say nearly 15,000 people in total cannot be located.
The Foreign Office would not say how many Britons were still missing.
But a spokesman said: "We are still working to locate British nationals whom we have been unable to contact. There are now a small number we remain very concerned for.
"It is important to stress that in these difficult circumstances it is likely to take some time for the Japanese authorities to formally identify those who may have lost their lives or been injured and to notify next of kin."
The Foreign Office is continuing to advise against all non-essential travel to areas to the north east of Tokyo.
Meanwhile, Britons at home have been digging deep to donate to emergency appeals set up by UK charities.
The British Red Cross has topped £6m, which will help the Japanese branch of the organisation fit out prefabricated house with rice cookers, microwaves and kettles.
The charity expects this to benefit some 280,000 people living in Miyagi, Fukushima and Iwate, some of the hardest hit areas.
Save the Children UK has raised £2.2m to help create 21 child-friendly spaces, mainly in Sendai.
World Vision UK was able to send £248,000 in donations to its staff based in Japan ensuring they could distribute clothes, blankets, bottled water and hygiene kits to those staying in evacuation centres.
And Islamic Relief gave nearly £40,000 in donations to a Japanese charity which distributed cooked food, hygiene kits, food staples and water tanks to thousands at an evacuation centre.
The Disasters Emergency Committee (DEC) - an umbrella body that represents 13 of the largest UK aid agencies - did not launch an appeal for Japan because it is a developed country and its government is among the best prepared in the world for disasters.