Seventeen people exposed to radiation after the poisoning of former KGB spy Alexander Litvinenko are continuing to be monitored five months on.
Mr Litvinenko's London home is still sealed up
All have been assigned a doctor, provide regular samples for testing and have been offered counselling.
After testing positive for polonium-210, they were told they had a greater long-term risk of cancer.
Among them were hotel staff and guests, and Marina Litvinenko. Her husband died in London last November.
A major public health investigation was launched by the Health Protection Agency after Mr Litvinenko's body was found to contain high levels of the radioactive substance polonium-210.
It is still ongoing and has cost £2m so far and involved hundreds of agency staff.
In all, more than 700 people in the UK have been tested for radiation.
Of those, 17 were found to have levels that were not high enough to cause illness in the short term, but in the long term there may be a very small increased risk of cancer.
Dr Michael Clark, of the Health Protection Agency, said: "The 17 are not likely to see any health effects in their lifetime.
"These people have not been poisoned, they have elevated levels of polonium-210 in their bodies which does slightly increase their risk of cancer later in life."
A further 673 people from 52 different countries were also tested.
Just three were found to have had possible contact with polonium-210, but their levels posed no risk to their health.
The Pine Bar at the Millennium Hotel remains closed
The HPA has also taken requests for particular individuals to be tested for radiation from the Metropolitan Police, which is investigating Mr Litvinenko's death.
The Millennium Hotel in Mayfair where he met his associate Dmitry Kovtun and his business partner Andrei Lugovoi, on 1 November 2006, emerged as being at the heart of the polonium trail.
Four guests at the hotel's Pine Bar and nine members of staff were among the 17 to test positive.
According to the hotel, all nine members of staff are still working there.
Others affected include two employees of the Sheraton Hotel, in Park Lane, who are both still working there, and one member of staff from Best Western Hotel in Piccadilly.
Tests for radiation were carried out at all three hotels, and a further 11 sites.
At the Millennium Hotel, the Pine Bar and several guest bedrooms remain shut while remediation work continues to seal or remove contaminated material.
However, it is understood that by the end of the month all except two sites where work has taken place, will be open.
Only Mr Litvinenko's London home, and offices in Grosvenor Street will remain shut, largely due to difficulties in tracing the property owners who live abroad.
Meanwhile, the police investigation in the UK is still continuing and some information has already been passed onto the Crown Prosecution Service.
The latest development in the independent investigation by Russian police was an interview with Russian billionaire, Boris Berezovsky.