SARAJEVO (Reuters) - A Soviet-era reconnaissance drone that crashed in the Croatian capital of Zagreb last month without causing any harm to residents carried an aerial bomb that exploded after hitting the ground, a panel of experts said on Wednesday.

       The investigators did not want to reveal the drone's intended target or who had sent it, but Hungary had said that the Tupolev TU-141 drone was detected by radar in Hungarian airspace after being detected over Ukraine, and had entered Hungary via Romanian air space.

       The drone, flying at 1,000 metres, flew from Hungary on March 10 and crashed seven minutes after entering Croatia's air space, the Croatian government had said.

       Both Hungary and Croatia are NATO members.

       The incident occurred two weeks after Russia invaded Ukraine in what it calls a "special military operation", which Western nations term an unprovoked attack.

       A detailed analysis of its metal fragments showed that the drone carrying an OFAB 100-120 aerial bomb hit the ground because of parachute failure, but no traces of military explosives, such as Trinitrotoluene (TNT), were found on it, Ivana Bacic, an expert on explosives, told a news briefing in Zagreb.

       The bomb was charged by unconventional organic powder which the explosion tore down to the gases so it was not possible to identify it, Bacic said.

       The investigators said 96 vehicles were damaged by the explosion near Jarun lake in Zagreb, estimated to have cost 600,000 kuna ($86,090).

       They declined to say who might have sent the drone and why, saying it was part of a defence ministry investigation.

       ($1 = 6.9694 kuna)

       (Reporting by Daria Sito-Sucic; Editing by Bernadette Baum)