For more than a year, Special Counsel Robert Mueller’s office has questioned witnesses broadly about their interactions with well-connected Russians. But three sources familiar with Mueller’s probe told The Daily Beast that his team is now zeroing in on Trumpworld figures who may have attempted to shape the administration's foreign policy by offering to ease U.S. sanctions on Russia.

The Special Counsel’s Office is preparing court filings that are expected to detail Trump associates’ conversations about sanctions relief—and spell out how those offers and counter-proposals were characterized to top figures on the campaign and in the administration, those same sources said.

The new details would not only bookend a multi-year investigation by federal prosecutors into whether and how Trump associates seriously considered requests by Moscow to ease the financial measures. The new court filings could also answer a central question of the Russia investigation: What specific policy changes, if any, did the Kremlin hope to get in return from its political machinations?

“During his investigation, Mueller has shown little proclivity for chasing dead ends,” said Paul Pelletier, a former senior Department of Justice official. “His continued focus on the evidence that members of the Trump campaign discussed sanction relief with Russians shows that his evidence of a criminal violation continues to sharpen. This has to come as especially bad news for the president.”

Mueller’s interest in sanctions arose, at least in part, out of his team’s investigation into former National Security Adviser Michael Flynn. The Special Counsel’s Office noted in a court filing last week that Flynn had lied to the FBI about his conversations with Russian Ambassador Sergey Kislyak concerning U.S. sanctions. But other portions of this court filing were left redacted.

Mueller’s team is looking closely at evidence—some of it provided by witnesses—from the transition period, two individuals with knowledge of the probe said.

“Sanctions conversations that happened after November are more serious,” said Angela Stent, a former national intelligence officer for Russia under President George W. Bush. “At that point Flynn, for example, would have already known he was going to be part of the administration and those conversations would have included plans for what might happen [next].”

And Flynn wasn’t the only figure talking sanctions during that transition period, three sources with knowledge of the probe said. Several individuals in Trump’s inner circle were developing their own plans to put pressure on other parts of the government to roll back the sanctions, which have cost the Russian economy more than $100 billion, according to Kremlin estimates.

It’s still unclear if Trump adviser Erik Prince and Kirill Dmitriev, the head of one of Russia’s sovereign wealth funds, spoke about sanctions in their now-infamous meeting in the Seychelles held during the last days of the transition. But The Daily Beast previously reported that the two spoke broadly about Russian investment opportunities in the U.S. and the potential for peace in Ukraine.

Just a week after Trump took office, Ukrainian lawmaker Andrii V. Artemenko handed Michael Cohen, then Trump’s personal lawyer, a “peace plan” that would lift sanctions. Accounts differ on how seriously the proposal was considered by the administration.

Around the same time, Trump reportedly asked staffers in the State Department to come up with a plan to roll back sanctions. But the department’s transition team was disorganized and understaffed, according to one person on the team. The request never made its way to people tasked with advising the White House on sanctions, according to two former national-security officials.

“The Russians were definitely looking to ease sanctions, or the relaxation of sanctions,” said one former Treasury official. “There was clearly a person they supported in the election and Trump clearly had a favorable view of Russia. But the transition was a mess and it took more time to get their feet under them. By the time they got their stuff together, Congress was increasing sanctions.”

The U.S. implemented sanctions on Russia in 2014 following its annexation of Crimea. Those sanctions were broadly supposed to make it more difficult for Russia to make money and to conduct business with the U.S. and its European allies. Several of Russia’s financial entities, including the Russian Direct Investment Fund, one of Moscow’s sovereign wealth funds, and VTB, one of the leading banks in the country, were put under sanctions but still allowed to transact with Americans under certain circumstances. Others, though, including top government officials like Igor Sechin, the CEO of Rosneft, the formerly state-owned Russian oil enterprise, were blacklisted.

When Trump began campaigning in 2015, the Russian sanctions had started to take a toll on local Russians. Trump, unexpectedly, vowed to roll them back. “I don’t think you’d need the sanctions,” the future president said in response to a question from Russian provocateur Maria Butina, who pleaded guilty this month to conspiracy to violate restrictions on foreign agents.

Meanwhile , Putin was in the midst of implementing measures to insulate the economy from total collapse, compliance lawyers told The Daily Beast. With the careful maneuvering of business deals, Russia continued to conduct business with the U.S. and its European allies, two former Obama officials involved in drafting the sanctions said.

But compliance lawyers said investors and U.S. businesses were wary of the legal risks of doing business with Moscow. The lifting of sanctions, lawyers told The Daily Beast, would have allowed for Russia to conduct business with American and European investors with more ease. It would have allowed international businesses and individuals to lend money to Russia as well as borrow, which the sanctions currently broadly restrict.

The topic kept coming up during the campaign. In the June 2016 meeting in Trump Tower with Russian lawyer Natalia Veselnitskaya , for example, Donald Trump Jr. reportedly suggested a review of sanctions law.

But since Trump took office, the Treasury Department has increased the number of sanctions on Russia. In April 2017, for instance, the government blacklisted another set of Russian oligarchs and government officials, many of whom have close connections to Russian President Vladimir Putin.

Congress is considering a number of pieces of legislation that would further punish Moscow for its interference in the 2016 elections.