Prosecutors in Kraljevo, Serbia began an investigation on Friday into three Kosovo officers who were controversially detained by the Serbian border control. The officers were arrested on Wednesday, and Serbian authorities are investigating whether they committed “[u]nauthorized production, possession, carrying and trafficking of weapons” while active on the Serbia-Kosovo border.

Kosovo’s Justice Minister Albulena Haxhiu called for the police officers to be released, alleging  Serbia “kidnapped” the officers within Kosovo. However, Serbian authorities suggest that the police officers were arrested on the Serbian side of the boundary, implying that the officers crossed the border intentionally. According to KFOR (the NATO peacekeeping mission in Kosovo), it still remains unclear where the Kosovo police officers were at the time of the arrest. Still, the US and UK have urged Kosovo and Serbia to de-escalate tensions and release the police officers.

Currently, tensions between Serbia and Kosovo are high after recent violent clashes between Kosovo police in the Serb-majority municipality Zvecan regarding the election of ethnic-Albanian mayors, which the Serbs boycotted. After, Serbia placed more troops on its side of the border, and Kosovo and NATO put authorities on the other. With this increased military presence, further protests began last week, and on Friday shock grenades exploded outside two Kosovo police stations in the country’s north.