BUCHAREST, Nov. 14 (Xinhua) -- Two sailors remain missing after their barge sank in the Danube after colliding with an Austrian tugboat on Friday, harbor authorities said.

    The tugboat and the 807-ton barge collided near the southeastern Romanian port of Calarasi.

    Several staff of the Emergency Inspectorate and the Environment Protection Agency have started removing leaking fuel from the sunken barge, said Harbor's Captain Anghel Constantin.

    "The Romanian barge carrying ballast was sailing upstream to Tulcea and sank with two sailors being aboard," Constantin said.

    The accident was most probably caused by a sailing error by the tugboat, Constantin said.

    Harbor authorities have started an investigation into the cause of the accident.

    The Danube, the longest river in the European Union, originates in Germany and flows eastwards for a distance of some 2850 km, passing through several Central and Eastern European capitals, before emptying into the Black Sea via the Danube Delta in Romania and Ukraine.

    Since the completion of the German Rhine-Main-Danube Canal in 1992, the Danube has been part of a trans-European waterway from Rotterdam on the North Sea to Romania's Sulina on the Black Sea.