Rep. Steny Hoyer of Maryland, the No. 2 Democrat in the U.S. House, said Wednesday that Jackson wasn't in "an unusual circumstance."
"People get sick, and when people get sick, they miss work. Everybody in America understands that," Hoyer said. "But I think the family would be well advised to give his constituents as much information as is appropriate."
Fellow Illinois Democrats Sen. Dick Durbin and Rep. Luis Gutierrez have called it Jackson's responsibility as a public official to disclose details. Jackson's little-known opponents in the November election have spoken out on the same issue, and some voters in his district have asked questions.
Durbin was unavailable for comment Wednesday evening after the Jackson office's latest statement.
Jackson spokesman Rick Bryant has said relatives requested Jackson's location be kept private, and his family has been unusually reticent on the issue. His wife, Chicago Alderman Sandi Jackson, has said little. And his father, civil rights leader Rev. Jesse Jackson Sr., has called it a private issue and repeatedly declined to give details.
The pending House Ethics Committee investigation is focusing on allegations that Jackson discussed raising money for Blagojevich's campaign so the then-Illinois governor would appoint him to President Barack Obama's vacated U.S. Senate seat. Blagojevich is serving a prison sentence for corruption. Jackson has denied the claims.
Jackson also allegedly directed a fundraiser, Raghuveer Nayak, to buy plane tickets for a woman described as Jackson's "social acquaintance." Jackson and his wife have called that a personal matter.
Nayak was the fundraiser arrested and charged with the unrelated medical fraud charges. He has pleaded not guilty.
At Blagojevich's 2010 corruption trial, prosecutors said another Blagojevich fundraiser was ready to testify that Jackson instructed Nayak to raise money for Blagojevich's campaign to help him secure the Senate seat. The same witness later testified he attended a meeting with Jackson and Nayak.
Jackson was not charged and has repeatedly denied wrongdoing.
Jackson faces a Republican and independent candidate in November, though he's widely expected to win re-election. He first won office in a 1995 special election and has easily won each race since. Jackson's district includes parts of Chicago and some suburbs but was expanded during the last redistricting process to include less familiar territory further south of the city.
Associated Press writers Donna Cassata in Washington and Jason Keyser in Chicago contributed to this report.
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