"We're going to proceed with all due speed, but we're going to make sure that what we do is done correctly," said Speaker Michael Madigan, who often has clashed with fellow Democrat Blagojevich.
Once the committee makes a recommendation, the full House will formally decide whether to file impeachment charges. The Senate then would rule on the charges.
Blagojevich was arrested Tuesday on federal fraud and bribery charges, including allegations of a scheme to profit from his power to appoint a replacement for the Senate seat vacated by President-elect Barack Obama.
The state constitution gives lawmakers broad authority to impeach a governor for any reason they consider sufficient.
The governor, who remains defiant and returned to work Monday to sign a tax credit bill, had no immediate reaction to the impeachment committee, spokesman Lucio Guerrero said after Madigan's announcement.
"Impeachment talk's nothing new for this governor," Guerrero said. "They've been talking about it for a long time."
Indeed, Madigan said Monday his staff has been reviewing the legal possibilities for impeachment for about a year. His office produced a memo earlier this year outlining all the arguments legislative candidates could make in favor of impeachment.
Blagojevich's administration has been under a federal corruption investigation for years.
Madigan was co-chair of Blagojevich's re-election campaign but more recently has been one of the governor's harshest critics. He often has refused to meet with Blagojevich or return his phone calls.
"I've had a chance to get to know Mr. Blagojevich over six years, so I was not surprised," Madigan said Monday of the federal allegations. "In light of what we've all seen ... how can anyone be surprised?"
However, Madigan did not join the chorus of officials calling for Blagojevich's resignation or indicate whether he thinks the governor should be impeached, saying he should remain neutral because he would preside over any impeachment debate.
If Blagojevich resigned, the power to appoint a new senator would go to Democratic Lt. Gov. Patrick Quinn.
Madigan's daughter, Illinois Attorney General Lisa Madigan, has asked the state Supreme Court to remove Blagojevich from office, arguing that he is unfit to serve. Madigan said Sunday she expects word on whether the court will hear her request "probably just in a few days."
Lisa Madigan is considered one of the top Democratic candidates for governor in 2010.
Renowned Chicago criminal defense attorney Ed Genson said Monday that if he's hired by Blagojevich he would represent the governor in any potential impeachment proceedings as well as his federal corruption case. Genson told The Associated Press he would know later Monday whether Blagojevich will retain him.
Michael Madigan made his announcement as lawmakers were preparing to meet to discuss legislation that would set a special election to fill Obama's Senate seat, stripping Blagojevich of the power to appoint the post.
Blagojevich hasn't ruled out the possibility of signing such a bill, Guerrero said.
While the special election was the stated purpose of Monday's legislative gathering, the day's early focus on impeachment came as no surprise.
David Dring, spokesman for House Minority Leader Tom Cross, had said Republicans would step up pressure on Democrats to remove Blagojevich, perhaps raising the issue on the House floor if necessary.
The GOP also planned television ads pressuring Democrats to approve a special election to replace Obama.
Illinois Republican Party chairman Andy McKenna told reporters the ads would "make the point that this is the people's seat, and the people deserve a special election."
Meanwhile, Rep. Danny K. Davis said Monday he had talked to Blagojevich three times since Obama's election to express his interest in Obama's U.S. Senate seat. He said the governor never made untoward suggestions.
The governor said things like "Oh Danny, you're one of the best, you're a great guy, you do great work plus you are serious about the needs of people and you know you're on the list. You're on the list,"' said Davis, who added he would run for the seat if there were a special election.
Davis said he didn't believe he is mentioned in the federal complaint against Blagojevich, which didn't identify potential candidates by name.
(Copyright 2008 by The Associated Press. All Rights Reserved.)