Irkutsk, August 1 (RIA Novosti, Alexander Batalin) - A new scientific expedition has set off for the crash site of a gigantic meteoroid that hit eastern Siberia, near the Vitim River, in September 2002.

Researchers investigating the crater said this might be their last chance to find large fragments of the bolide, which they hope will provide them with some vital information about the space impact threat. The previous three expeditions yielded nothing but cosmic dust grains.

Irkutsk University Observatory Director Sergei Yazev, who is leading the fourth expedition to the Vitim meteoroid crash site, said his team would be following a new itinerary, drawn up after meticulous study of the seismic waves recorded by local monitoring stations during the incident.

Yazev said expedition participants will also try to solve the mystery of a hillside pyramid spotted in the area back in 1949. The pyramid, with a crater on top, is believed to be either the result of the impact of a super-dense celestial body or the result of a powerful volcanic eruption.