MEXICO CITY (AP) — Mexican President Claudia Sheinbaum responded sharply Thursday to U.S. government sanctions blocking transfers from three Mexican financial institutions, saying Washington hasn't shown evidence of its allegations of money laundering.

The U.S. Treasury Department announced the sanctions Wednesday on the banks CIBanco and Intercam Banco and the brokerage Vector Casa de Bolsa, alleging that they had facilitated millions of dollars in money transfers for Mexican drug cartels.

Sheinbaum said during her morning news briefing Thursday that the administration of U.S. President Donald Trump had showed no evidence proving that the institutions carried out any money laundering, despite repeated requests for such evidence.

“The Treasury Department hasn't provided a single piece of evidence to show that any money laundering was taking place," she said. “We aren’t going to cover for anyone, there isn’t impunity here. They have to be able to demonstrate that there was actually money laundering, not with words, but with strong evidence."

The accused banks also fired back on the orders, rejecting the allegations and similarly citing a lack of evidence.

Brokerage firm Vector said Wednesday night in a statement that it “categorically rejects any allegation that compromises its institutional integrity" while Intercam said in a statement it denies being involved in any “illegal practice.” Vector is owned by entrepreneur Alfonso Romo, who served as chief of staff to ex-President Andrés Manuel López Obrador early in his presidency.

Manuel Somoza, president of strategies of CIBanco, told local press that they only heard about the order the same time it was made public, and noted that it wasn't a formal legal accusation, but rather an investigation.

“Our books are open," he said. ”Rumors are clearly damaging, whether they’re true or not. So, what we want is for (American authorities) to come and investigate."

Sheinbaum said they were notified by American officials of the accusations ahead of the Wednesday announcement, and that Mexican financial regulators carried out their own investigations into the institutions.

They found "administrative infractions," she said, but nothing close to the accusations being levied by Treasury officials.

In the orders blocking transactions between the three institutions and American banks, the Trump administration alleged that the three companies facilitated millions of dollars in transfers with Chinese companies, which it said were used to buy chemicals to produce fentanyl. The Treasury Department said the institutions had facilitated transfers to U.S. banks, but officials would not name which U.S. institutions were implicated nor provide more details.

Sheinbaum countered that their own investigation simply showed that institutions had strong relationships with Chinese clients and banks, which she said was more of an indicator that the two countries share a robust trade relationship. China has been the main source of chemical precursors to produce fentanyl in Mexico, according to U.S. authorities. At the same time, the U.S. has increasingly sought to block growing Chinese influence and investment in Latin America.

The leader also expressed frustration on Thursday morning, reminding Trump officials that Mexico is a sovereign nation and must be treated as an equal by the U.S. government.

“We're no one's piñata," she said. "Mexico must be respected.”