We know that the Israelis used American "bunker-buster" bombs on Hizbollah's Beirut headquarters. We know that they drenched southern Lebanon with cluster bombs in the last 72 hours of the war, leaving tens of thousands of bomblets which are still killing Lebanese civilians every week. And we now know - after it first categorically denied using such munitions - that the Israeli army also used phosphorous bombs, weapons which are supposed to be restricted under the third protocol of the Geneva Conventions, which neither Israel nor the United States have signed.

But scientific evidence gathered from at least two bomb craters in Khiam and At-Tiri, the scene of fierce fighting between Hizbollah guerrillas and Israeli troops last July and August, suggests that uranium-based munitions may now also be included in Israel's weapons inventory - and were used against targets in Lebanon. According to Dr Chris Busby, the British Scientific Secretary of the European Committee on Radiation Risk, two soil samples thrown up by Israeli heavy or guided bombs showed "elevated radiation signatures". Both have been forwarded for further examination to the Harwell laboratory in Oxfordshire for mass spectrometry - used by the Ministry of Defence - which has confirmed the concentration of uranium isotopes in the samples.

Dr Busby's initial report states that there are two possible reasons for the contamination. "The first is that the weapon was some novel small experimental nuclear fission device or other experimental weapon (eg, a thermobaric weapon) based on the high temperature of a uranium oxidation flash ... The second is that the weapon was a bunker-busting conventional uranium penetrator weapon employing enriched uranium rather than depleted uranium." A photograph of the explosion of the first bomb shows large clouds of black smoke that might result from burning uranium.

Chris Bellamy, the professor of military science and doctrine at Cranfield University, who has reviewed the Busby report, said: "At worst it's some sort of experimental weapon with an enriched uranium component the purpose of which we don't yet know. At best - if you can say that - it shows a remarkably cavalier attitude to the use of nuclear waste products."