Former President Donald Trump's lawyers and advisers are trying to figure out if there is evidence and witnesses they are unaware of that are bolstering special counsel Jack Smith's investigation into efforts to overturn the 2020 election, according to multiple sources familiar with Trump team's legal conversation.

The potential charges listed in the target letter suggest the special counsel will prosecute a bigger case against Trump than the former president's team was expecting, given the evidence they are aware of. That has led to questions if there is evidence or testimony they don't know about, the sources said.

Trump's team of lawyers and advisers have tried to keep close tabs on investigation. The former president's political action committee has underwritten legal costs for multiple witnesses, which has given them some insight into what has been shared with Smith's team.

Trump said on social media Tuesday that he received a target letter from Smith on Sunday, a signal that charges in the case could be coming soon.

The target letter cites three statutes that Trump could be charged with: pertaining to deprivation of rights; conspiracy to commit an offense against or defraud the United States; and tampering with a witness, according to multiple news outlets, including The Wall Street Journal, which cited a person familiar with the matter.

The Justice Department has been known in the investigation to be examining possible violations of the law around conspiracy and obstruction of the congressional proceeding on January 6, which is part of the witness tampering law, CNN previously reported following a Justice Department search of a Trump administration adviser's home.