A Mexican drug cartel was so bold in operating frauds that target elderly Americans that the gang's operators posed as U.S. Treasury Department officials, U.S. authorities said Thursday.

The scam was described by the department's Office of Foreign Assets Control, or OFAC. The agency has been chasing fraudsters using call centers controlled by the Jalisco drug cartel to promote fake offers to buy Americans' timeshare properties. They have scammed at least 600 Americans out of about $40 million, officials said.

But they also began contacting people claiming to be employees of OFAC itself, and offering to free up funds purportedly frozen by the U.S. agency, which combats illicit funds and money laundering.

"At times, perpetrators of timeshare fraud misuse government agency names in attempts to appear legitimate," the agency said. "For example, perpetrators may call victims and claim to represent OFAC, demanding a payment in exchange for the release of funds that the perpetrator claims OFAC has blocked."

Officials have said the scam focused on Puerto Vallarta, in Jalisco state. In an alert issued in March, the FBI said sellers were contacted via email by scammers who said they had a buyer lined up, but the seller needed to pay taxes or other fees before the deal could go through.

"The sales representatives often use high-pressure sales tactics to add a sense of urgency to the deal," the FBI said.

Apparently, once the money was paid, the deals evaporated.

OFAC announced a new round of sanctions Thursday against three Mexican citizens and 13 companies they said are linked to the Jalisco cartel, known by its Spanish initials as the CJNG, which has killed call center workers who try to quit.

U.S. Treasury Secretary Janet L. Yellen said in the statement that "CJNG uses extreme violence and intimidation to control the timeshare network, which often targets elder U.S. citizens and can defraud victims of their life savings."

The Jalisco cartel is better known for producing millions of doses of deadly fentanyl and smuggling them into the United States disguised to look like Xanax, Percocet or oxycodone. Such pills cause about 70,000 overdose deaths per year in the United States.

"Treasury remains committed to the Administration's whole-of-government effort, in coordination with our partners in Mexico, to disrupt CJNG's revenue sources and ability to traffic deadly drugs like fentanyl," Yellen said.

In June, U.S. and Mexican officials confirmed that as many as eight young workers were confirmed dead after they apparently tried to quit jobs at a call center operated by the Jalisco cartel.

While the victims' families believed their children worked at a normal call center, the office was in fact run by Jalisco, Mexico's most violent gang.

The Department of Justice has called the Jalisco cartel "one of the five most dangerous transnational criminal organizations in the world." The cartel's leader, Nemesio Oseguera, aka "El Mencho," is among the most sought by Mexican and U.S. authorities.

In:
• Mexico
• Cartel