Slovenia confirmed Monday the existence of a mass grave that could contain the bodies of several thousand German and Nazi collaborator troops killed by the communists at the end of World War II. 'Taking into account the size of the mass grave, it could contain the bodies of several thousands victims that were killed in May and June 1945,' Marko Strovs, the head of a government commission in charge of investigating mass graves, told Slovenian news agency STA. He added that a research team last week carried out ground tests in the Mostec area, situated in eastern Slovenia close to the border with Croatia, and found evidence confirming the existence of skeletons piled in a mass grave. The mass grave is some 186 metres long (610 feet), between 3.5 to four metres wide, and the layer of skeletons is estimated to be 1.2 metres deep, Strovs told STA. 'It is evident that the victims died violently,' Strovs said. He added that the mass execution must have been carried out following the 'Russian pattern' of undressing the prisoners before executing them in order to hide their identities. A public prosecutor who took part in the ground testing will decide on the next steps at the site, Strovs said. People from the Mostec area believed that numerous German soldiers along with pro-Nazi Slovenian and Croatian troops and other sympathisers had been killed after World War II, and then thrown into an anti-tank trench and buried, Slovenian media reported. The Slovenian authorities started in 2008 a long-running investigation of over 500 suspected mass graves throughout Slovenia. They are believed to contain the remains of pro-Nazi collaborators who sought to escape from the former Yugoslavia's communist regime in 1945. Slovenia was part of Yugoslavia before becoming independent in 1991. 