Materials available to the US secret services show that the al-Qaida terrorist organisation formed by Osama bin Laden managed to have at its disposal radioactive materials the amount of which is sufficient for making a radioactive dispersion device which experts call the "dirty bomb". The Newsweek received this information on Monday from representatives of American secret services who preferred not to be named. If exploded in the centre of a densely populated city the "dirty bomb" does not destroy as much as when nuclear weapons are used. It disperses radioactive substances in the air with the help of explosives. The Newsweek does not report any additional details about this weapon, but earlier US experts provided materials to mass media that the "dirty bomb" is dangerous also because after its explosion a considerable territory may become uninhabited for many decades. Last week the White House circulated an official warning that a group of former nuclear weapons scientists from Pakistan met with Osama bin Laden and Mullah Omar in 2001 and handed in information to them about the use of radioactive substances for manufacturing nuclear weapons. It is also known that soon after this meeting one of al-Qaida representatives declared that he managed to receive access to a certain radioactive substance, the press service of the White House reported.