Relations between Russia and the West are turning frosty following the downing of a Malaysian Air passenger jet near the Russian border with Ukraine.

The U.S. and European Union countries have escalated sanctions on top individuals in Russia and added sanctions affecting the financial, oil and military sectors.

Now comes the news that passengers aboard a Silversea Cruises ship were denied entry at a small port in the Russian Pacific. Why they stayed on the ship remains murky.

A preponderance of the passengers on the Silver Discoverer, a small expedition ship, are from the U.S., Great Britain, Germany and Australia, and the local Siberia Times quotes a Russian tour organizer in the port of Provideniya saying that orders denying them entry “allegedly” came from Moscow.

A spokesman for the Russian security service told a Russian news website that the passengers lacked the necessary paperwork.

In a statement, Silversea said its ship had received all the necessary clearances for passage into the Chukotka area of Russia and guests and crew had been cleared by immigration, but on arrival July 28, they were denied landing by the Russian authorities.

Spokesman Brad Ball said the line was given no explanation at all.

The ship was sailing a 12-day itinerary from Seward to Nome and was scheduled to call in the Chukotka region on the final few days of the voyage. A new itinerary has been established in Alaska for the rest of the trip.

Port calls in the nearby region of Kamchatka are still being permitted.

If this is merely a regional matter, the impact is limited because relatively few cruise ships visit Pacific Russia. But other regions are more important. Royal Caribbean Cruises Ltd. has said demand for cruises in the Black Sea the rest of this year has been “strained” by Russian’s annexation of Crimea.

Travelers considering a Baltic cruise should keep a close eye on things lest sanctions affect debarkations in St. Petersburg, the crown jewel of the cruise industry’s Baltic trade.