The Trump administration escalated sanctions against Venezuela’s oil industry, targeting four maritime companies for supporting the “illegitimate” government of President Nicolas Maduro. The Treasury’s Office of Foreign Assets Control also identified four tankers it said had continued to lift oil cargoes from Venezuelan ports in recent months as blocked property, according to a statement on Tuesday. Three of the companies are based in the Marshall Islands and one is based in Greece, according to Treasury.

“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,” Treasury Secretary Steven Mnuchin said. “The United States will continue to target those who support this corrupt regime.”

The companies targeted are Afranav Maritime Ltd., the registered owner of the Athens Voyager; Seacomber Ltd. which owns Chios I; Adamant Maritime Ltd., which owns Seahero; and Sanibel Shiptrade Ltd., which owns Voyager I. Emails to media officials at the national oil company Petroleos de Venezuela SA and the oil ministry were not immediately returned.

All property and interests in the entities that are in the U.S. or in possession of U.S. citizens are also blocked.