WASHINGTON (CNN) -- The House Ethics Committee announced Wednesday it wants more time to gather information in the investigation of alleged ethics violations by three House members -- Minnesota GOP Rep. Michele Bachmann, Illinois GOP Rep. Peter Roskam, and New York Democratic Rep. Tim Bishop.
The panel closed its investigation of allegations made against Massachusetts Democratic Rep. John Tierney.
Members of the ethics panel, which is evenly split between Republicans and Democrats, made the announcement after completing a 90-day review of reports filed by the non-partisan Office of Congressional Ethics (OCE).
Bachman, who is not running for re-election next year, is facing accusations of an improper transfer of campaign funds to help her 2012 White House bid. Among other things, Bachmann may have improperly used funds from a leadership PAC to pay a campaign consultant, according to the OCE.
In its report -- which was released by the Ethics Committee on Wednesday -- the OCE also said Bachmann may have improperly used campaign resources to promote the sale of her book, Core of Conviction.
The four-term congresswoman also faces allegations over her presidential campaign's failure to reveal payments to an Iowa state senator who worked on Bachmann's behalf. In its report, however, the OCE recommended that the House Ethics Committee dismiss that charge, arguing that there is no "substantial reason" to believe that Bachmann knew disclosure reports filed with the Federal Election Commission by her presidential campaign were false.
Bachmann has repeatedly denied any wrongdoing. In July, her attorney blasted the OCE for making "highly politicized allegations" that are "baseless and without merit."
Meanwhile, Roskam, a member of the House GOP leadership, is being investigated for a trip that he and his wife took in the fall of 2011 to Taiwan.
The key question in the case is whether Roskam's trip was run by the government of Taiwan or an educational organization known as the Chinese Culture University. House rules ban travel paid for by foreign governments.
Roskam spokeswoman Stephanie Kittridge noted in a statement released in July that the ethics committee itself approved of the trip, and insisted the OCE was wrong to review a matter that had been vetted through appropriate channels.
Bishop, now in his sixth term, is under fire for allegedly soliciting a $5,000 campaign donation from a supporter in return for helping the supporter's family get a permit to set off fireworks at their son's bar mitzvah celebration.
In July, Bishop declared, "I welcome a fair-minded review of the facts because I have done nothing wrong."
Tierney, a nine-term congressman, had been accused of breaking rules relating to public financial disclosure.
Tierney's wife received over $220,000 while managing a bank account for her brother, who ran an illegal offshore gambling operation. She spent a month in prison after pleading guilty to helping her brother file false tax returns.
Tierney, who faced a tough re-election fight in 2012, argued his wife's payments were a gift not subject to disclosure rules.
In its statement released Wednesday, the Ethics Committee's top Democrat and Republican called the evidence in Tierney's case "inconclusive."
CNN's Deirdre Walsh contributed to this report.