Hungarian security operatives administered a “forced injection” to one of the Ukrainians detained earlier this month during a dramatic raid on bank vehicles carrying gold bars and tens of millions of dollars and euros in cash, sources have told the Guardian.

Hungary’s TEK anti-terrorism police detained seven Ukrainians from the state savings bank, Oschadbank, on 5 March. They were accompanying a convoy of two armoured cars from Vienna to Ukraine, as it transited Hungary in what Kyiv claims was a regular transfer of state funds. Hungarian officials have claimed it was money for the “Ukrainian war mafia”, without giving details.

The men were held for more than 24 hours, much of which they spent blindfolded and in handcuffs, before they were deported to Ukraine. During that time, one of the men – a former employee of Ukraine’s SBU security service – was given the forced injection, security sources in Kyiv said.

The sources added that they believed the injection contained a relaxant that was meant to predispose subjects towards becoming talkative during interrogations. However, the drug reportedly led the man, who is diabetic, to have a hypertensive crisis and lose consciousness. He was eventually taken to hospital.