Federal Security Service (FSB) Col. Gen. Andrei Burlaka is believed to be the highest-ranking Russian official linked to the investigation into the downing of Flight MH17, according to a joint investigation by the investigative outlet Bellingcat and Russia’s The Insider news website published Tuesday.

Dutch-led investigators have so far named four pro-Russian separatists as suspects in criminal proceedings into the deaths of 298 people aboard Malaysia Airlines Flight MH17, which was shot down over eastern Ukraine in July 2014. The investigation appealed for witnesses last fall to help name a key figure identified as “Vladimir Ivanovich” in intercepted calls with separatist commanders. 

Bellingcat and The Insider identified “Vladimir Ivanovich” as Col. Gen. Andrei Ivanovich Burlaka, the FSB Border Service’s chief of operational staff. The outlets said that they established Burlaka’s identity through extensive searches of phone records, travel data and voice-comparison technology.

This FSB general is the highest-ranking Russian official identified as a person of interest in the criminal investigation into the downing of MH17,” Bellingcat wrote.

It noted that Burlaka is two steps removed from FSB chief Alexander Bortnikov, who answers directly to President Vladimir Putin.

BBC Russia corroborated Burlaka’s identity through an unnamed source who had personally spoken with Burlaka.

Bellingcat said that Burlaka was “in a crucial position to supervise the movement of weapons from Russia to Ukraine, and thus would have had to authorize the transfer of the Russian Buk missile launcher that shot the Malaysian airliner after crossing the border.

Based on the call intercepts as a whole, it becomes clear that ‘Vladimir Ivanovich’ played a critical role in the chain of command between ostensibly local militants and the Russian government,” it wrote.

Russia has denied any role in the July 17, 2014, downing of MH17.