The team investigating the crash of Malaysian Airlines Flight MH17 said that fragments found in the eastern Ukraine, where the aircraft went down, might include parts from a Russian Buk surface-to-air missile system.

The Joint Investigation Team (JIT) looking into the MH17 crash released a statement Tuesday that “several parts, possibly originating from a Buk surface-air-missile system” were being investigated. A number of media reports said that the fragments originated from a “Russian-made” missile system.

JIT spokesman Wim de Bruin, however, said that it was “too early to draw any conclusion.” It will take “forensic investigation to establish whether these parts … were parts of a Buk [missile] system or not,” he told Russia Today. He added that it would be difficult to say when final reports would turn up.

According to de Bruin, the only thing that was clear was that those fragments had been found in eastern Ukraine. But, he said, there was no “causal connection between the discovered parts and the crash of flight MH17,” he said in the statement.

The BBC earlier reported that, according to Dutch investigators, the fragments were “suspected” to be from a Russian missile system. However, it was also reported that the investigators had not found any “causal connection” yet.

Dutch prosecutors believe those fragments were part of the criminal investigation looking for more information about who was behind the MH17 crash.

According to Ukraine and a number of Western countries, pro-Russian separatists shot the Malaysia Airlines flight down in eastern Ukraine. It is also believed that the rebels might have used a Russia-supplied Buk missile system.