A Republican colleague of disgraced ex-Congressman Mark Foley confronted him about his e-mails with teenagers as early as 2000, a US newspaper reports.
Mark Foley denies ever having sexual contact with a minor
A young congressional worker had shown Jim Kolbe inappropriate messages from Mr Foley, the Washington Post said.
The report comes as a congressional panel investigates claims Republican leaders knew of Mr Foley's explicit e-mails years ago, but took no action.
The scandal is dominating politics ahead of mid-term elections next month.
Correspondents say that if claims the Republican leadership knew about Mr Foley's messages were to be proven, the party's chances of holding on to Congress after the poll would be greatly reduced.
On Saturday the head of the Republican House campaign committee launched a TV commercial in which he apologised for not doing more to "catch his [Mr Foley's] lies".
Tom Reynolds repeated his claim that he told House Speaker Dennis Hastert about Mr Foley's behaviour in the spring.
"I trusted that others had investigated. Looking back, more should have been done, and for that, I'm sorry," Mr Reynolds said.
Mr Hastert has apologised over the row, denied any early knowledge of the e-mails and ruled out resigning.
Mr Foley, a member of the House caucus on missing and exploited children, resigned last month following recent revelations that he had sent lurid e-mails to young male staff.
The Washington Post report suggests his communications with pages - high school students appointed to help with administrative work in the House - were known to other lawmakers five years earlier than previously acknowledged.
A spokeswoman for Mr Kolbe told the newspaper that a former page had shown the Arizona congressman internet messages from Mr Foley, saying they had made him uncomfortable.
Mr Kolbe's press secretary, Korenna Cline, told the Post that a Kolbe staff member advised the page last week to discuss the matter with the clerk of the House.
Ms Kline denied the messages were sexually explicit and said "corrective action" was taken, although she did not know whether that went beyond Mr Kolbe's confrontation with Mr Foley.
The ethics committee of the House of Representatives has launched an inquiry into who became aware of the allegations and when, although it has no jurisdiction over Mr Foley.
The youngest recipient of the suggestive e-mails is said to have been 16 years old.
Mr Foley - through his lawyer - has denied any sexual contact with minors.