Treasury Department officials were using a secret Gmail back channel to communicate with the Russians at the same time the Kremlin was seeking sensitive financial information on its enemies, including several of Hillary Clinton’s backers, during the 2016 election, according to a report Thursday.

Russia’s financial crimes agency, set up by Russian President Vladimir Putin in 2001, has close ties to the country’s espionage network. It made a request for sensitive documents on Dirk, Edward, and Daniel Ziff, who had run afoul of the Kremlin, BuzzFeed News reported.

The request was made weeks before Russian lawyer Natalia Veselnitskaya met with members of Trump’s campaign at Trump Tower, where she offered “dirt” on Clinton, including her links to the Ziff brothers.

Russian agents also tried to pressure the Americans to hand over private financial documents on at least two dozen dissidents, academics, private investigators, and American citizens, according to BuzzFeed News.

The requests were made as Treasury Department officials were using their government email accounts to communicate with the Russian government’s unofficial email accounts, despite being warned that the Russians were “manipulating the system” to conduct “fishing expeditions.”

Analysts raised fears of the Treasury’s internal systems being compromised by viruses in the emails from the unofficial Russian accounts, but officials continued to use the back channel into 2017.

The Treasury Department would not confirm or deny why the back channel continued to be used as Russia made the suspicious requests or whether it turned over any information to the Russians.

“Treasury does not discuss or comment on confidential communications with foreign governments, including to confirm whether or not they have occurred. We have notified our Office of the Inspector General of these allegations,” it said in a statement to the news outlet.