BUCHAREST, Romania (AP) — Authorities in Romania have opened a criminal investigation against four employees of the local branch of neighboring Serbia's NIS Petrol — which is majority-owned by Russia's Gazprom Neft — over suspected data leaks.

Organized crime prosecutors said late on Monday that police raided the company's offices in the capital, Bucharest, and the western city of Timisoara, along with the employees' homes, as part of the probe.

No other details were immediately released. The Associated Press has sent a request for comment to NIS Petrol.

Late on Monday, Serbia's President Aleksandar Vucic said no Serbian citizens were involved and that “this has nothing to do with us, its Russia's ownership."

Romanian media reported the four are citizens of Moldova and high ranking in the Romanian subsidiary of NIS petrol.

Serbia sold the majority stake in its state oil monopoly NIS to Russia's Gazprom Neft in 2008. The Balkan nation still maintains close relations with Russia despite the aggression on Ukraine and has refused to join Western sanctions against Moscow.

NIS Petrol in Romania runs Gazprom gas stations in the west of the country and has carried out exploration for new sources of oil. The Romanian prosecutors said information about geological data had been sent to Belgrade and to Russia before Romanian authorities were informed.