Nord Stream AG starts its own investigation into the gas pipeline leaks in the Baltic Sea. A “specially equipped ship” arrived at the site of the accident in the Swedish economic zone, the consortium, which is majority-owned by the Russian company Gazprom, announced on Thursday.

According to the Swedish Navy, the ship sailed under the Russian flag.

The owners of Nord Stream 1 informed the Swedish authorities about their plans a few weeks ago, Swedish Navy spokesman Jimmie Adamsson told AFP. No approval from the Swedish authorities is required for use in the Swedish economic zone.

Nord Stream AG said it would take an estimated three to five days to investigate the leaks. The consortium is also awaiting permission from the Danish authorities to inspect the leaks in the Danish economic zone.

Four leaks were discovered in the Nord Stream 1 and 2 gas pipelines from Russia to Germany off the Danish island of Bornholm at the end of September, two in the Swedish and two in the Danish economic zone. According to an official Danish-Swedish report, the leaks were caused by violent explosions.