That source said federal investigators were seeking campaign records of "anything that [Williams] touched" financially.
Williams, a Democrat serving his second four-year term in office, did not respond Thursday to voice mail and email requests for comment. A message also was left with the District Attorney's Office.
Lisette Gonzalez, executive director of Friends of Seth Williams, declined to respond when asked three times during an interview Thursday if she received the subpoenas.
"I don't like talking to the media. I'm not answering your questions," Gonzalez said before hanging up.
Billy Miller, a political consultant who works for Williams, said he knew nothing about any subpoenas. Miller referred questions to Matt Haverstick, an attorney representing Williams.
Haverstick, who has served as treasurer and on the board of directors of Second Chance Foundation, a nonprofit founded by Williams, did not respond to requests for comment.
A spokesman for the District Attorney's Office said no subpoenas had been served there.
The most recent campaign report for Friends of Seth Williams, filed in February to detail finances for 2014, showed that he started the year with $50,962, raised $83,475 in contributions, and spent $116,518, leaving $17,919 in the bank as of Dec. 31.
The report details $28,446 Williams spent at the Union League of Philadelphia for dues, meals, and a campaign fund-raiser. He also spent $4,603 on cellphones and $2,175 on membership dues for the Sporting Club at the Bellevue.
Williams, in a statement of financial interests filed in April, listed only the U.S. Department of Education as a creditor. He listed as sources of income his job as district attorney, Villanova University Law School, Temple University Law School, and the Army Reserve.
Questions about Williams' personal finances have been raised before.
His campaign made payments of $12,707 to his wife, Sonita, during his first run for district attorney in 2005. Sonita Williams filed for bankruptcy that year, citing $71,000 in credit-card debt.
Williams lost that bid but was successful in 2009. His campaign reported payments of $9,762 to his wife that year. Williams defended the payments, calling them reimbursement for his own expenses.
The couple, who have three daughters, announced in December 2011 that they were divorcing.
Williams fell behind on his Philadelphia Gas Works bill in April 2012, prompting the utility to file a lien in Common Pleas Court for $578.73. Williams paid his bill the following month.
He was sued in Municipal Court in August 2012 by a collection agency seeking payment for an outstanding Lowe's credit-card bill. A judgment of $1,826.56 was entered against Williams a month later.
Williams has made prosecuting public corruption cases a priority as district attorney.
He hired former prosecutors from the state Attorney General's Office, who picked up and pursued cases against six elected officials, all Democrats, from Philadelphia.
That investigation, which focused on alleged bribes offered by a lobbyist working as an informant for prosecutors, started in the state Attorney General's Office. The cases were ultimately dismissed as unwinnable by Kathleen G. Kane, a Democrat who took office as attorney general in 2013.
After the investigations were taken up by the Philadelphia District Attorney's Office, three state representatives - Ron Waters, Michelle Brownlee, and Harold James - pleaded guilty, along with former Traffic Court Judge Thomasine Tynes. Two representatives, Vanessa Lowery Brown and Louise Williams Bishop, are fighting the corruption charges in court.
The case has set off a war of words between Williams and Kane, with each questioning the motives and actions of the other.
Kane was charged this month with perjury and other crimes, accused of leaking secret grand jury material to the Philadelphia Daily News.
Williams served as a top aide to then-District Attorney Lynne M. Abraham, whom he considered a career mentor. He resigned and then challenged Abraham unsuccessfully in the 2005 Democratic primary.
Abraham did not seek reelection in 2009, when Williams prevailed in a five-person primary and then easily won the general election.
He was elected to a second term in 2013 with 81 percent of the vote.
Williams, who has been talked about as a possible replacement for U.S. Rep. Chaka Fattah - indicted last month on federal corruption charges - would be up for reelection in 2017 for a third term.
Inquirer staff writer Craig R. McCoy contributed to this article.