Berezovsky death: Chemical hazard police search house
24 March 2013 Last updated at 07:03 GMT
Police with expertise in environments contaminated with chemical, biological and nuclear material have been involved in a search of the house of the late Boris Berezovsky.
The exiled Russian tycoon, aged 67, was found dead on Saturday, and a Thames Valley police cordon remains in place as police investigate his unexplained death.
Bridget Kendall reports.