A stretch of water off the coast of southern Greece that had become a pivotal logistics hub in the Russian oil supply chain has suddenly been abandoned by the tankers that had been flocking there.

When sanctions were placed on Russian supplies, the Laconian Gulf became a key spot for switching cargoes between vessels. It enabled some ships to shuttle to and from Russian ports, and others to do the long-distance voyages to buyers in Asia. However, it also sparked environmental concerns about the risk of an oil spill in a picturesque European bay.   

Since the start of this month, vessels appear to have left the gulf but are instead clustered just to its south, according to TankerTrackers.com Inc. The firm cross-referenced signals from ships with an analysis of satellite imagery.

There are other signs of change in how Russian oil is moving. One tanker also flipped a cargo of crude onto another vessel in the Red Sea last month. The Panta Rei 1 transfered its cargo onto the Odysseus, which then transported its consignment to India. That’s the first ever switch observed in that location in ship tracking data compiled by Bloomberg.

It was unclear why the shift in southern Greece happened. Ships can move as a result of bad weather. However, the Laconian Gulf has hills all around it, offering some protection from the wind and calm waters. That has made it a useful spot for transferring cargoes and helps to reduce environmental risks. 

On a trip to the Port of Piraeus this week, Greek Shipping Minister Christos Sylianides said the safety of the country’s shipping is above all other things.