Russian investigators have launched a criminal probe into two prison officials for their suspected role in the 2009 death of a jailed lawyer, Sergei Magnitsky.

The chief physician at Moscow's Butyrskaya prison, Larisa Litvinova, and the prison's deputy chief, Dmitry Kratov, are suspected of negligence in Magnitsky's death.

Magnitsky, who worked for a London-based investment fund (Hermitage Capital Management) claimed to have uncovered a $230-million tax fraud plot by corrupt Interior Ministry officials.

But he was arrested and jailed in 2008 by the same people he had accused in the corruption scheme. While in jail Magnitsky developed pancreatitis, but his requests for medical care were mainly ignored. He died in November, 2009 at the age of 37, after nearly a year in prison.

The announcement of the probe has not satisfied Magnitsky's supporters, who say the investigation is not going after the real guilty parties. Some Western nations have viewed Magnitsky's case as a test of Russia's commitment to rooting out corruption.