Fattah's lawyer, Luther E. Weaver 3d, said that he had not obtained a copy of the subpoena, but that it clearly was part of an ongoing investigation that he said began about seven years ago.
"I recently was retained, but I understand that they have been looking at things for that time," said Weaver, a former federal prosecutor who has been a defense lawyer in a number of well-publicized cases, including this year's federal prosecution of the founder of the former Raising Horizons Quest Charter School.
Patricia Hartman, the chief spokeswoman for U.S. Attorney Zane David Memeger, said her office would "neither confirm nor deny the existence or nonexistence of an investigation."
The city declined to confirm that it had received a subpoena.
Fattah's office in Washington did not respond to requests for comment.
One current and one former federal investigator, both speaking on condition of anonymity, confirmed that Fattah has been of interest to federal authorities here for years.
They said that a routine part of an investigation of a public official is to determine whether other people are paying the bills of that official. Investigations sometimes go for years and end with no charges filed by prosecutors.
The subpoena asked for all records since 2008 relating to properties Fattah and his wife have owned in Philadelphia.
One property cited in the subpoena is a home the congressman owns in the 5700 block of Nassau Road, near Lancaster Avenue in West Philadelphia. Fattah bought that house for $28,000 in 1981, records show. Taxes are $1,169 a year.
Fattah and his wife now live in a $400,000 home near Philadelphia University in East Falls.
Last year, the couple purchased a 4.8-acre Pike County home in the Poconos for $425,000. Pike County officials said they had not received any subpoena for records related to that property.
Fattah's son, Chaka Jr., has also been under investigation by federal authorities for income tax and bank loan issues - a probe that surfaced in February 2012 when FBI agents searched his home and office and confiscated records. Friends of the congressman in May started a defense fund for the younger Fattah, saying the family was unable to keep up with the legal bills.
Lawyer George Burrell, who was a top aide to Mayor John F. Street and is trustee for Fattah Jr.'s defense fund, said Thursday that less than $5,000 in donations had been received in the last five months.
The extent to which the investigations are connected is not clear.
The elder Fattah, 56, was reelected last fall to his 10th two-year term representing a district that sprawls from South Philadelphia and Center City to Northwest Philadelphia and Lower Merion Township in Montgomery County.