Russian tycoon Boris Berezovsky.<br /> <br />A fierce critic of President Vladimir Putin, the former mathematician was found dead at his home in Britain on Saturday.<br /> <br />British police said the death was unexplained and began an investigation on Sunday, using officers trained to detect chemical, biological, radiological and nuclear tampering.<br /> <br />Sixty-seven-year-old Berezovsky, once a member of the Kremlin's political elite, helped Putin rise to power, only to become his sworn enemy and flee into exile in Britain.<br /> <br />Associates say the businessman may have committed suicide or suffered a heart attack after losing a 6 billion US dollar court case to football club owner, Roman Abramovich.<br /> <br />Some residents in the Russian capital Moscow seemed largely unaffected by news of Berezovsky's death.<br /> <br />(SOUNDBITE) (Russian) MOSCOW RESIDENT ANDREI, SAYING:<br /> <br />"Who cares? Really. The man has not lived in Russia for so many years, and in fact he was thrown away from here. Who cares? I'm
