BOGOTA, Colombia — The U.S. Treasury is advising banks to be on the lookout for suspicious financial activity involving corrupt Venezuelan officials as the Trump administration tightens its financial noose around President Nicolas Maduro’s embattled socialist government.

Wednesday’s advisory by the Financial Crimes Enforcement Network asks banks to keep watch for Venezuelan government contracts, wire transfers from shell companies and real estate purchases in south Florida and Houston by senior Venezuelan officials, their families or associates. It said the advisory arose out of concern expressed by financial institutions that transactions involving state-owned enterprises were being used to launder kickbacks and bribes.

U.S. officials fear that endemic corruption will take an additional toll on Venezuelans already struggling with triple-digit inflation and widespread shortages amid a tense political standoff aggravated by Maduro’s decision to rewrite the constitution in the face of months of deadly protests.

Last month, the Trump administration slapped sanctions on Venezuela for Maduro’s decision to go forward with his plans to consolidate power. The actions ban investors from buying the nation’s debt and prevents U.S.-based Citgo, a subsidiary of the state-owned oil company, from sending badly needed dollar dividends back to Venezuela.

“Not all transactions involving Venezuela involve corruption, but, particularly now, during a period of turmoil in that country, financial institutions need to continue their vigilance to help identify and stop the flow of corrupt proceeds and guard against money laundering and other illicit financial activity,” said Acting FinCEN Director Jamal El-Hindi.

Maduro has accused the U.S. of trying to impose a financial “blockade” on Venezuela after the opposition-led protests failed to oust him from power. Even before the recent round of sanctions, many Wall Street banks like Citibank and Credit Suisse that used to collect large fees serving Venezuela’s financial needs stopped doing business with the government, fearing legal action or damage to their reputations.

Wednesday’s action lists several red flags to assist banks in identifying suspected schemes. They include any transactions involving government contracts payable directly to personal accounts, hard-to-identify trading companies and involving products charged at substantially higher prices than market rates.

It also warns about real estate purchases — primarily in south Florida and the Houston area — involving current or former Venezuelan government officials, family members or associates that are not commensurate with their official salaries.

The U.S. over the past year has sanctioned dozens of Venezuelan officials, including Maduro himself, for a variety of alleged offenses including drug-trafficking and human rights abuses. Among the state-owned enterprises referenced in recent sanctions are the nation’s electricity and telephone companies as well as the foreign trade bank and foreign currency exchange commission that provides U.S. dollars to select businesses and individuals at a highly favorable exchange rate that most Venezuelans can’t access due to strict currency controls