A second sanctioned Russian oil tanker has resurfaced again after a month-long absence from digital vessel-tracking systems that made it harder to know what the ship did with its cargo.

Automated tracking signals from the Bratsk, sanctioned by the US Treasury’s Office of Foreign Assets Control in February, resumed on Friday off the south coast of Oman, vessel tracking data compiled by Bloomberg show. Its sister ship, the Belgorod, appeared in a similar spot on Tuesday.

Both are heading to the Red Sea, the route back toward ports in the west of Russia.

The ships both loaded cargoes of about 1 million barrels of Russia’s flagship Urals crude at the Black Sea port of Novorossiysk in May and June, according to shipping information seen by Bloomberg. 

They were initially picked up by automated tracking systems as they left the Black Sea through Turkey’s Bosphorus shipping strait and were tracked on their voyages across the Indian Ocean to locations south of India, where automated tracking signals halted.

One of the two was observed carrying out a ship-to-ship transfer with the supertanker Oxis in the Gulf of Oman earlier this month by TankerTrackers.com Inc, which specializes in detecting secretive cargo movements

Definitively identifying which one, though, is tricky because the Bratsk and the Belgorod share the same dimensions and are essentially indistinguishable from above. Its possible both did so.

Sovcomflot previously declined to comment on transfers onto the Oxis.

Even though it was in the Gulf of Oman, the Oxis was sending a signal showing it as being anchored in the Strait of Hormuz, close to Iran’s Jask oil terminal. 

The Oxis is now heading toward the Malacca Strait, which ships pass through en route to Asia.

Neither the Bratsk nor the Oxis has updated its draft to show if a cargo switch took place, something that the crew does manually.

Moscow has begun putting some of its sanctioned tankers back into operation, testing the effectiveness of sanctions imposed on them by the US, the UK and the European Union. 

It means that three vessels have now hauled Russian crude toward Asia and apparently moved their cargoes onto other tankers to make it more difficult to track the origin of the oil when it’s delivered. It also shields buyers from association with sanctioned vessels.