The illness of the Russian former security agent Alexander Litvinenko is unlikely to have been caused by thallium poisoning, the hospital doctors treating him have said.
Dr Amit Nathwani, the consultant caring for Mr Litvinenko at University College Hospital in London said further tests would be conducted to establish the cause of his condition.
The latest twist in the extraordinary Cold War-style saga came after a leading toxicologist claimed that Mr Litvinenko could have been poisoned with "radioactive thallium".
In a statement, the hospital trust said: "Mr Litvinenko is being treated in the intensive care unit of University College Hospital so he can receive cardiac monitoring and specialist support in areas such as nutrition and pain relief.
"He can also be more effectively isolated to protect him against infection, following the damage to his immune system.
"We have requested toxicology tests to establish what poisoned Mr Litvinenko. Based on results we have received today and Mr Litvinenko's clinical features, thallium poisoning is an unlikely cause of his current condition.
"Further tests will be carried out to establish whether or not there is a single cause for Mr Litvinenko's condition."
Professor Henry said Mr Litvinenko, 43, had symptoms consistent with thallium poisoning but other symptoms linked to other substances.
Dr Henry, speaking outside University College Hospital, said if it was radioactive thallium it would now be difficult to trace.
He said Mr Litvinenko's bone marrow was not functioning and his white cell count has dropped to zero.
"Something other than thallium is involved... at this stage radioactive thallium seems the most likely cause," he said.
Radioactive thallium is used in hospitals, but Dr Henry said it was not used in massive doses consistent with Mr Litvinenko's condition.
Кто знает что за хрень - у таллия есть ещё радиоактивный изотоп и им тоже можно отравить, или же есть только один таллий - и о нем была всё время речь? Или это вообще ни фига не таллий?