The staff of the Russian embassy engaged in financial transactions last year that raised red flags at their bank, prompting the bank to alert Treasury officials, Special Counsel Robert Mueller has learned.

According to Buzzfeed News, which says its reporters have reviewed documents related to the transactions, former Russian ambassador to the U.S. Sergey Kislyak was paid $120,000 in mid-November, just days after the shock election of Donald Trump. Citibank filed a so-called “suspicious activity report” for the transaction in part because it did not seem to match previous payroll disbursements, Buzzfeed reports. Kislyak, who has since returned to Russia, was the official with whom fleeting National Security Advisor Michael Flynn had undisclosed contacts, leading to Flynn’s guilty plea in December. Moreover, Kislyak is the official with whom White House advisor/Trump son-in-law Jared Kushner discussed setting up a secure communications channel linking the White House and the Kremlin, bypassing the State Department and other traditional channels.

Elsewhere, the documents are said to reveal that Citibank rejected a withdrawal from the embassy’s account in the amount of $150,000 just five days after the inauguration in January. A flurry of payments in the spring of 2014, simultaneous to a referendum on Crimea seceding from Ukraine and joining Russia, has also drawn scrutiny, as have significant payments–some $2.4 million over several years–to a small construction firm run by a Russian immigrant.

“All the transactions which have been carried out through the American financial system fully comply with the legislation of the United States,” Nikolay Lakhonin, a spokesperson for the Russian embassy, told Buzzfeed. “We see such leaks by U.S. authorities as another attempt to discredit Russian official missions.”

The news that Mueller is looking at Russian Embassy transactions comes a month after a Bloomberg report, vigorously rebutted by Trump lawyer Jay Sekulow, that the special counsel’s office subpoenaed financial records for Trump’s business associates from Deutsche Bank.