Two more people in London have tested positive for radioactive polonium-210, the substance believed to have killed ex-Russian agent Alexander Litvinenko.
Mr Litvinenko died in London on 23 November 2006
A staff member at the Best Western Hotel, Piccadilly, and a guest at the Millennium Hotel's Pine Bar in Mayfair were affected, health officials said.
Levels were not enough to result in any short-term illness and risks in the long term were very small, they said.
A total of 12 people in London have now tested positive for radioactivity.
Others to have tested positive for polonium-210 include eight members of staff at the Millennium Hotel, a member of staff at the Sheraton Hotel on Park Lane and Mr Litvinenko's wife, Marina.
Mr Litvinenko visited the Millennium Hotel for a meeting with three Russian men - Dmitry Kovtun, Andrei Lugovoi and Vyacheslav Sokolenko - on 1 November last year.
All three deny any involvement in the death of Mr Litvinenko.
A spokesman for the Health Protection Agency (HPA) said a further 536 urine samples had so far been tested with none showing any cause for concern.
Mr Litvinenko died in London on 23 November and his body was found to contain a massive dose of the radioactive isotope polonium-210.
A statement made by Mr Litvinenko before he died accused Russian President Vladimir Putin of involvement in his death.
But the Kremlin has dismissed any suggestion it was involved as "sheer nonsense".