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WASHINGTON — Democratic pressure on Rep. John Conyers, D-Mich., to resign from Congress mounted Tuesday as the number of sexual harassment allegations against him continued to grow and party leaders huddled in conversations about whether he should remain in the House, multiple sources tell NBC News.

A report in The Detroit News on Tuesday detailed allegations from a woman who said that the congressman engaged in aggressive sexual behavior toward her while she worked in his congressional office. Those allegations follow similar ones from other women and an admission last week from the congressman that he had reached a settlement with one of them.

In an additional sign that Democrats were dropping their support of Conyers, House Minority Leader Nancy Pelosi sent a letter to the House Ethics Committee, which has opened an investigation into the allegations against Conyers, urging it to act "expeditiously" in their investigation.

The Congressional Black Caucus, which was co-founded by Conyers, will hold its regularly scheduled meeting Wednesday, but in an unusual move, staff will not be allowed in the room and Conyers was not sent an invitation to attend, one source told NBC News.

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A photo posted to Twitter appeared to show Conyers boarding a flight Tuesday night from Washington to Detroit.

Rep. Pramila Jayapal, D-Wash., a member of the Judiciary Committee that Conyers held a ranking position on until he stepped down on Sunday, said Tuesday that Conyers "must resign."

"No one ever wants to believe that someone they respect and have regarded as a champion for civil rights issues would abuse their power to harm and harass women," Jayapal said in a statement. "It is not easy for me to reach this conclusion because, as a civil rights activist, I have looked up to Rep. Conyers for decades. I believe these women, I see the pattern and there is only one conclusion — Mr. Conyers must resign.”

Jayapal follows Rep. Kathleen Rice, D-N.Y., who called for Conyers' resignation last week.

The Congressional Black Caucus chairman, Rep. Cedric Richmond, D-La., said in a statement Tuesday that he met with Conyers and "we had a very candid conversation about the seriousness of the allegations against him, which he vehemently denies."

"Any decision to resign from office before the ethics investigation is complete is John’s decision to make," Richmond said in the statement.

Deanna Maher told The Detroit News that Conyers made unwanted sexual advances against her shortly after she was hired in 1997.

Maher told the paper Conyers put his hand up her dress and assigned her to stay in his hotel room during work travel.

Maher is the second woman to come forward publicly to detail mistreatment by Conyers. The first was Melanie Sloan, who runs a congressional ethics watchdog group in Washington, who told The Washington Post that Conyers was abusive during her time as his counsel at the Judiciary Committee.

BuzzFeed reported last week that one woman who settled a sexual harassment claim with Conyers in 2015 outside of the House’s Office of Compliance for $27,000.

Conyers admitted to the settlement, which he paid out of his office funds, but has denied any wrongdoing.