Israeli experts have arrived in southern Russia to assist the investigation into what caused a Russian airliner to explode and crash Thursday into the Black Sea. The disaster killed 78 people on board the plane that may have been hit by a Ukrainian missile.

The Israeli specialists will assist their Russian counterparts who have been examining pieces of wreckage from the air disaster in the southern city of Sochi.

Most of the victims were Israeli citizens of Russian origin who were traveling on a regularly scheduled flight from Tel Aviv to Siberia.

Evidence indicates the plane could have been hit by a Ukrainian surface-to-air missile, which was being test-fired at the time.

Officials say some of the wreckage includes material that could not have come from the plane.

Russian Defense Minister Sergei Ivanov says President Vladimir Putin is not satisfied with the information provided by Ukrainian defense officials.

Mr. Ivanov has asked Ukraine for more specific information about the trajectory of SS-200 missiles, as well as controls over their firing.

Soon after the crash, the U.S. military said a satellite had detected a plume of smoke near the place where the Russian jet was flying.

The Russians have also asked the Pentagon to provide more details of that evidence to assist in the investigation.

Originally Russian leaders indicated the disaster could have been an act of terrorism. But Israeli officials discounted that, given the strict security procedures that were followed at Ben-Gurion airport near Tel Aviv before the plane left.

Apart from wreckage, more than a dozen bodies have also been recovered, most of them burned beyond recognition.

Many relatives of the victims are also in Sochi, trying to identify their loved ones in a city morgue.