Millions of dollars have been siphoned from Venezuela’s state oil company into a small bank almost 6,000 miles away, in Bulgaria, officials there said on Wednesday as they disclosed an investigation into suspected money laundering.

The Bulgarian government has frozen accounts at the bank, and is looking into accounts at other institutions as well, the officials said at a news conference in the capital, Sofia. But much of the money wired from Venezuela, they said, has already been transferred to accounts outside of Bulgaria.

United States authorities tipped off the Bulgarians to the transfers from Petróleos de Venezuela, or Pdvsa, the state oil company, American and Bulgarian officials said. The Trump administration, which is trying to force President Nicolás Maduro from power amid a deepening political crisis, recently imposed economic sanctions on the company.

Dimitar Georgiev, the head of the State Agency for National Security, said of the amounts involved, “We can’t be exact, but millions of euros.”