U.S. officials say they are keeping tabs on a vessel they believe is a Russian spy ship in international seas off the coast of Hawaii, where tensions between the United States and Russia remain high due to Russia’s involvement in the conflict in Ukraine.

U.S. Coast Guard officials stated in a press release that they have been keeping an eye on a Russian ship off the coast of the Hawaiian Islands for the past few weeks because of concerns that it may be collecting intelligence.

The Coast Guard has said this is not an unusual occurrence, but that it is still keeping a tight eye on the situation. Foreign-flagged military vessels have been observed operating and loitering within Coast Guard District Fourteen’s area of response, the release said.

“While foreign military vessels may transit freely through the U.S. economic exclusive zone (EEZ), as per customary international laws,” the release continued.

It’s not the first time vessels suspected of being Russian spies have been spotted near American shores. Two US officials told CNN that a Russian surveillance ship was seen in 2019 operating in a “unsafe way” near the southeast coast of the United States.

Unsafe behaviour was observed aboard the Russian surveillance ship Viktor Leonov as it sailed off the coasts of South Carolina and Florida. The ship was not using running lights during periods of poor visibility and was not responding to commercial vessels’ attempts to communicate to avoid collisions.

The US Coast Guard said in a press release that it “continues to coordinate with Department of Defense partners, giving updates to foreign vessel movements and activities and to appropriately meet presence with presence to encourage international maritime rules.”