Russian officials spoke with Sofia Thursday via video conference, saying the South Stream project posed no threat to the environment or ecology in the Black Sea, the Sofia News Agency reported.

South Stream is intended to eventually replace a portion of the Blue Stream pipeline from Russia to Turkey. South Stream will travel 560 miles through the Black Sea from Russia to the Bulgarian port of Varna.

Grigoriy Velcheck with the science and research division of Russian energy giant Gazprom, which holds a major stake in South Stream, said evidence gathered from the construction of the subsea portions of Blue Stream suggested there would be no harm to plant or animal species.

Georgi Hebaum of the Bulgarian Central Lab for General Ecology, however, said South Stream posed a significant risk to several species of mussels and seaweed.

South Stream is a rival to the Western-backed Nabucco pipeline, though development of South Stream is in doubt because of environmental and financial concerns.