British doctors say the health of an Italian contact of former Russian spy Alexander Litvinenko has improved, after radioactive material was found in his body.

Officials say security expert Mario Scaramella tested positive for traces of polonium-210 - the same material found in the body of Litvinenko after his death. Traces of the material also have been found in Litvinenko's wife.

Before he died last month, Litvinenko accused Russian President Vladimir Putin of ordering his murder. Moscow denies the charges.

Russia's Defense Minister Sergei Ivanov Saturday pledged full cooperation with a probe into Litvinenko's death.

Meanwhile, a Finnair plane was briefly delayed in Moscow after officials said radiation was found on board. Later tests found no radiation.

In Britain, radiation has been detected on five planes that recently flew into London's Heathrow Airport.

Radiation also was found in several other locations in London, including a sushi restaurant where Litvinenko ate before getting ill.

Litvinenko had been investigating the murder of famous Russian journalist Anna Politkovskaya in October. She was a frequent critic of the Kremlin and its policies in the separatist republic of Chechnya.

Some information for this report provided by AP and AFP.