TRACES of the radioactive poison used to kill former Russian spy Alexander Litvinenko were last night discovered at Arsenal's Emirates Stadium.

Businessman and ex-KGB agent Andrei Lugovoy, a crucial witness in the poisoning investigation, went to the north London football ground to watch Arsenal play CSKA Moscow in a Champions League game on November 1.

He is one of three Russians who met Litvinenko at the Millennium Hotel in London on the afternoon he was poisoned with polonium-210.

Premiership giants Arsenal only moved into Emirates Stadium this season.

A Health Protection Agency spokesman said the quantity of radiation found at the stadium was "barely detectable" and that there was no risk to public health.

In other developments, the Italian academic who met with Litvivenko was discharged from hospital today.

A London University College Hospital spokesman said Mario Scaramella was well and showing no symptoms of radiation toxicity.

In Moscow, Lugovoy was yesterday admitted to hospital over fears he too had been struck down by the killer substance.

But he said he had been given permission to speak to Scotland Yard detectives who have travelled to the Russian capital.

The interview will take place under the supervision of the chief Russian prosecutor's office and Russian officials are expected to conduct the questioning.

According to The Times, Russian authorities have demanded Britain hand over the enemies of president Vladimir Putin who have been given asylum in London in exchange for help in their investigation.

The results of Litvinenko's post-mortem examination is unlikely to be released before next week.