As many as 10 Sharpton associates were subpoenaed Wednesday to testify before a federal grand jury in Brooklyn on Dec. 26, his lawyer told the Daily News.
"Here we go again," Sharpton, whose various ventures have come under scrutiny before, told the New York Post. "Whatever it is, it's part of the territory. I'm a public figure."
Sharpton's associates were told to provide investigators with financial records from the campaign and roughly six Sharpton-related businesses, as well as personal financial documents of Sharpton and his wife, the newspaper said.
The FBI and Internal Revenue Service are seeking the records, which go back to 2001, according to the Daily News.
A Sharpton spokeswoman did not immediately return phone calls or e-mail messages from The Associated Press early Thursday.
An FBI agent who answered the phone at the agency's New York headquarters declined to comment, and an agency spokesman did not immediately return a telephone message. An IRS spokesman did not immediately return phone calls.
"It was like a sting or a raid," said Carl Redding, Sharpton's chief of staff for eight years during the 1990s. "They converged on everybody."
Redding said FBI agents awoke him at 6:30 a.m. Wednesday with a subpoena to testify and to bring records to the grand jury, but would not tell him the reason for the investigation.
Several staffers from the National Action Network, a Sharpton-led civil rights organization, also got subpoenas to testify, said Sharpton lawyer Michael Hardy. Sharpton himself did not receive a subpoena, the Daily News said.
Sharpton spokesman Charlie King said the minister and the National Action Network were cooperating with the probe. He said he had "zero idea, not a hint" what the authorities were looking for.
"The irony of this is we've been working with a number of government agencies to make sure that we're up to speed on all of our outstanding paperwork," he said.
"When you're in the midst of civil rights like this, it's nothing new," King said. "Dr. [Martin Luther] King went through it, and Rev. Sharpton has been through it before," reports the New York Post.
Hardy was sanguine about the developments. "I can't think of a time when the Rev. Sharpton wasn't under investigation," he said.
Sharpton agreed in 2005 to repay the government $100,000, plus interest, for taxpayer money he received during his failed effort to win the Democratic presidential nomination the year before, though he denied wrongdoing.
The Federal Election Commission had determined that he spent more of his own money on the campaign than the qualifications for federal matching funds allow.
In 1993, Sharpton pleaded guilty to not filing a state income tax return in 1986.