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WASHINGTON (CNN) – A House ethics panel says it is investigating allegations against three representatives including Jesse Jackson Jr., who allegedly launched a "public campaign" to be appointed to President Barack Obama's former Senate seat.

The preliminary investigation into Jackson's activities by the Office of Congressional Ethics became known in April. At the time, Jackson, an Illinois Democrat, issued a statement saying he was cooperating and was "eager to answer any questions and provide any information to the OCE about my actions related to last year's vacant Senate seat."

The House ethics panel, the Committee on Standards of Official Conduct, said in a statement Tuesday it had received a referral on the matter from the ethics office.

Transcripts of recordings from former Illinois Gov. Rod Blagojevich "contain statements that an 'emissary' from Representative Jackson had offered to raise money for Blagojevich and provide 'money up-front' if Blagojevich nominated Representative Jackson to the (U.S.) Senate seat vacated by President Obama," the ethics office report says. "If this 'emissary' acted either at the direction of Representative Jackson or with his knowledge and acquiescence, Representative Jackson may have violated federal law and House rules."

However, the Department of Justice asked that the committee defer investigating the matter because of the criminal indictment against Blagojevich and its investigation into "the facts surrounding Rod Blagojevich's consideration of multiple candidates to fill the Senate seat," the House ethics panel said in its statement.

Because of that request, the investigation will be deferred, the statement said, but "the committee will continue to monitor the situation and
will consider pursuing avenues of inquiry that it concludes do not interfere with the activities of the Department of Justice."

The Office of Congressional Ethics was created by the House in March 2008 to screen cases of potential improper conduct by representatives. A board of six members, who are outside experts, meets monthly to review issues and votes on whether to recommend that the Committee on Standards of Official Conduct launch a formal investigation. The committee then decides whether to take up the matter.

The other two lawmakers being investigated are Reps. Maxine Waters, D-California, and Sam Graves, R-Missouri. The committee issued separate statements for each of them. The statements do not disclose the allegations being investigated.

Blagojevich earlier this year was impeached and removed from office. He has pleaded not guilty to federal corruption charges. A federal grand jury in April indicted him on 16 felony counts including racketeering, conspiracy, wire fraud and making false statements to investigators.

Democratic leaders had urged Blagojevich not to appoint anyone to Obama's vacant seat. He disregarded their counsel and named Roland Burris, a former state attorney general and state comptroller, to the seat. Democratic senators grudgingly recognized him as the junior senator from Illinois, but he still faced an investigation and scrutiny at the same time he was trying to learn the ropes on Capitol Hill.

In June, the state's attorney in Sangamon County, Illinois, said he would not charge Burris with perjury in connection with his testimony on
Blagojevich's alleged "pay for play" scheme to fill the Senate seat. John Schmidt, the state's attorney, said Burris gave incomplete but truthful answers to questions about his conversations with Blagojevich's representatives.

Burris said in July he will not run for a full six-year term in 2010.

The indictment against Blagojevich also named Christopher Kelly, Blagojevich's chief fundraiser. Kelly, 51, died Saturday at a hospital.
Officials have said his death is being investigated as a suicide.

–CNN's Deirdre Walsh contributed to this report