New York prosecutors have convened a grand jury that is expected to decide whether to indict former president Donald Trump, suggesting they may have found evidence of a crime, US media are reporting.
The development is the latest step towards Mr Trump, who left the White House in January, possibly becoming the first former US president to face criminal charges.
In the US, prosecutors typically refer important cases to grand juries made up of citizens who examine the prosecution's case in secret.
They hear evidence and can request additional documents before deciding whether criminal charges should be brought.
Mr Trump fired off a statement in response to the reports, rejecting the investigation as "purely political" and "a continuation of the greatest witch hunt in American history".
"It's never stopped," he said. "No other president in history has had to put up with what I have had to."
The grand jury will sit three days a week for six months, according to The Washington Post.
The panel is also hearing several matters unrelated to Mr Trump's case, the paper reported.
It said the move, also reported by ABC, suggests that Manhattan District Attorney Cyrus Vance may have found evidence of a crime, if not by Mr Trump then somebody close to him.
A spokesman for Mr Vance refused to comment when contacted by AFP.
Mr Vance and New York state Attorney General Letitia James, both Democrats, are investigating Trump's business dealings – prompting the Republican to claim he is being persecuted.
"This is purely political, and an affront to the almost 75 million voters who supported me in the Presidential Election, and it's being driven by highly partisan Democrat prosecutors," Mr Trump said.
Investigators are examining whether the Trump Organisation committed tax evasion, insurance and bank fraud.
Mr Vance's investigation initially focused on hush payments made to two women who allege they had affairs with Mr Trump – but the investigation has since been expanded.
Investigators suspect the Trump Organisation may have artificially inflated and reduced the value of assets, particularly several properties in New York state, to either get bank loans or reduce their taxes.
Last week, Ms James said her office was investigating the Trump Organisation in a "criminal capacity" and was working with Mr Vance's team.
The Trump Organisation did not respond to an AFP request for comment on Tuesday.
Mr Vance, who leaves his post at the end of December, acquired eight years of Mr Trump's tax returns in February after a years-long legal battle that went to the Supreme Court.
Investigators are notably looking into the remuneration of key executives at the Trump Organisation, according to The Washington Post.
According to several media, Mr Vance's team has been looking closely at the Trump Organisation's long-serving chief financial officer, Allen Weisselberg, one of the family's most loyal servants.
Investigators believe Mr Weisselberg knows all of the Trump family secrets and have been putting pressure on him for months to co-operate with their investigation.
Observers are closely watching whether Mr Weisselberg will turn against his former boss.
Trump's ex-personal lawyer Michael Cohen – jailed for tax evasion and breaking campaign finance laws – was one of his closest henchmen before turning against his former boss and deciding to co-operate with prosecutors.
