The US Treasury Department announced Tuesday that four companies have been blacklisted for aiding the Venezuelan regime’s efforts to transport oil to the US market.

The Office of Foreign Assets Control (OFAC) placed Adamant Maritime Ltd, Afranav Maritime Ltd, Sanibel Shiptrade Ltd and Seacomber Ltd on the specially designated nationals list.

Treasury Secretary Steve Mnuchin said Tuesday, “the illegitimate Maduro regime has enlisted the help of maritime companies and their vessels to continue the exploitation of Venezuela’s natural resources for the regime’s profit.” Mnuchin added that the US government will keep sanctioning companies that aid the Venezuelan regime.

Consistent with OFAC guidelines, the assets of the four companies have been blocked and others will be prohibited from engaging in business with them.

US President Donald Trump’s administration has implemented a number of sanctions on Venezuela since 2017, citing “authoritarian policies, intolerance for dissent, and violent and systematic repression of human rights and fundamental freedoms.”