Uranium was embedded in metal bars seized at Heathrow

Officials say there is no threat to public but it is unclear whether radioactive element was deliberately concealed

A discovery of metal bars embedded with uranium at Heathrow in late December has triggered an urgent counter-terrorism investigation, in an attempt to establish why it was concealed in an aeroplane shipment.

Scotland Yard said on Tuesday night the amount of contaminated material was extremely small" and posed no threat to the public" although some reports had suggested, incorrectly, that several kilograms of uranium itself were discovered.