Russian investigators have said they could not identify the source of polonium.

The Georgian side accused Russian investigators in the lack of cooperation with the investigation.

So far, however, there has been no follow-up by Russian investigators.

Although now divorced, he said, he and his former wife remain close, and she has agreed to meet with Russian investigators.

These are the first interviews in the case that Russian investigators are known to have made on British soil.

He said the Russians did not deny their guilt to Russian investigators who visited them.

This would allow Russian investigators to pinpoint how far the missile could have flown.

In 1995, the same Russian investigators published findings from 740 patients with advanced cancer.

Both have been questioned by Russian and British investigators.

Russian investigators have told their American counterparts they believe that crime groups in Russia exercised some form of control over the operation.