Several Russian tankers reportedly turned off their tracking systems 33 times last week, a practice the US says could be used to evade sanctions

According to location data provided by Windward, Russian tanker ships switched off their tracking systems at least 33 times last week. The normal weekly rate is double that.

This tactic known as "going dark" or "dark activity" has been flagged by the US Treasury as one of several deceptive practices used to evade sanctions in the maritime industry.

The data from Windward shows that ship-to-ship meetings are taking place that could take a long time to transfer cargo to vessels without sanctions.

Windward said last week that 22 unique vessels have entered Russian waters for the first time since the invasion of Ukraine.

The news follows reports that several of the Russian tycoons who owned the superyachts turned off their tracking signals last week.

Automatic identification system (AIS), also known as tracking technology, must be installed on all vessels of 300 gross metric tons or more that sail on international voyages.

International convention requires certain classes of vessels to broadcast their location signal at all times.

In a sanctions advisory last May, the US Treasury warned thatvessels engaged in illegal activities may also try to hide their movements by disabling their transponders.

The US and UK have banned Russian oil and Russian vessels from entering their ports. The sanctions against Russians have led to a flurry of highly-scrutinized ship movement as owners attempt to escape seizure.

It could be harder for companies to avoid doing business with people who are on a sanctions list if location data is turned off on ships.

Everyone in yachting is scared. Sam Tucker of the market intelligence firm VesselsValue previously told Insider that the penalties of dealing with Russians are very high.