Grand jury in Georgia expected to convene in probe of Trump's efforts to overturn election

A grand jury is expected to be seated this week in Fulton County, Georgia, to look into efforts by Donald Trump to overturn the 2020 election, signaling that the county's investigation into the former president is intensifying.

Prosecutors in Fulton County are expected pursue subpoenas for documents and witnesses and rely heavily on them, people familiar with the investigation told ABC News.

In a letter sent last month from Fulton County District Attorney Fani Willis to Gov. Brian Kemp and obtained by ABC News, Willis said the grand jury would convene in March and would "begin requesting grand jury subpoenas as necessary at that time."

Willis wrote in the Feb. 10 letter that her office had no reason to believe any Georgia official was the target of the investigation.

The district attorney's office in Fulton County formally launched a criminal probe into Trump's efforts to overturn his election loss in the state last month, after Trump was heard in a Jan. 2 phone call pleading with Georgia Secretary of State Brad Raffensperger to help him "find 11,780 votes," the exact number he needed to win Georgia.

"This investigation includes, but is not limited to, potential violations of Georgia law prohibiting the solicitation of election fraud, the making of false statements to state and local governmental bodies, conspiracy, racketeering, violation of oath of office and any involvement in violence or threats related to the election's administration," Willis wrote in her letter to the governor.

George Washington University Law Professor John F. Banzhaf, whose formal complaints with Georgia officials helped trigger the investigation, says that Trump's hour-long call to Raffensperger could have violated as many as three separate state laws.

Trump has previously denied any wrongdoing.

ABC News' Quinn Scanlan contributed to this report.