The Serbian border police seized half a ton of cocaine at the Gostun border crossing with Montenegro, Podgorica daily Vijesti said on Thursday.

Vijesti sources in the Montenegrin National Security Agency said that the drugs were seized from a man from the Serbian town of Loznica who owns a company registered in the Montenegrin town of Danilovgrad and added that the cocaine was hidden in a tanker truck. The date of the seizure was not specified.

Law enforcement agencies on both sides of the border are investigating the case, the daily said.

At least two organized crime groups based in Montenegro have been involved in cocaine smuggling over the past few years.

The Serbian Customs Administration said the Vijesti report was premature because the tanker was still being examined. “Efforts to safely open the gas-filled tanker to determine its contents are underway and once it is open we will know what is inside and issue a statement,” a press release said.