Investigators for special counsel Robert Mueller have recently been asking witnesses about Donald Trump’s business activities in Russia prior to the 2016 presidential campaign as he considered a run for president, according to three people familiar with the matter.

Questions to some witnesses during wide-ranging interviews included the timing of Trump’s decision to seek the presidency, potentially compromising information the Russians may have had about him, and why efforts to brand a Trump Tower in Moscow fell through, two sources said.

The lines of inquiry indicate Mueller’s team is reaching beyond the campaign to explore how the Russians might have sought to influence Trump at a time when he was discussing deals in Moscow and contemplating a presidential run.

Mueller was appointed to investigate Russian meddling in the 2016 campaign. The President claims that any investigation of his family’s finances would be a breach of the special counsel’s mandate.

Two of the sources said they do not know from the questions asked whether Mueller has concrete evidence to indicate wrongdoing.

“You ask everything even if you don’t think it’s credible,” one of the sources said, adding, “the allegations are out there, and it was checking the box.”

The special counsel’s office, an attorney for the President and the Trump Organization all declined to comment for this story.

Questions about Trump’s entry into the campaign

Investigators asked one witness when Trump became serious about running for President, a person familiar with the matter said, adding that investigators seemed very interested in when Trump actually decided to run and how that coincided with his business ventures.

The source said the witness told Mueller’s team his impression was that Trump was serious about running back in 2014. Trump tweeted earlier this month that he “didn’t know” that he was going to run for president in 2014.

This witness was also asked whether Russians had been seen in the office at Trump Tower New York prior to 2015. The answer was no.

Questions have also touched on the possibility of compromising information that Russians may have or claim to have about Trump, according to two sources familiar with the matter. That subject matter echoes claims in a controversial dossier written by a former British spy who was paid by an opposition research firm underwritten by Trump’s Democratic opponents.

Questions about Trump’s Moscow trip

Several lines of questioning to witnesses have centered on the 2013 Miss Universe pageant, which was held in Moscow, and unsuccessful discussions to brand a Trump Tower Moscow, two sources said.

For the pageant, Trump partnered with Aras Agalarov, and his son, Emin Agalarov, billionaire real estate developers in Russia. In congressional testimony last year, Donald Trump Jr. said that “preliminary discussions” to build a tower in Moscow began between the Trump Organization and the Agalarovs after the Miss Universe pageant. Trump tweeted with excitement about the potential project, saying “Trump Tower-Moscow is next.”

But the plans fell through. Rob Goldstone, a publicist for pop star Emin Agalarov, told Yahoo News last year that the Trump Tower deal was scrapped because “the economy tanked in Russia” from harsh sanctions imposed by Western countries.

Mueller was appointed last spring to investigate Russian meddling and “any matters that arose or may arise directly from the investigation,” according to the order signed by Deputy Attorney General Rod Rosenstein, a Trump appointee.