The House Ethics Committee announced Wednesday that it will drop its investigation of Rep. John Tierney (D-Mass.), having found "inconclusive" evidence that he failed to disclose his wife's income on his financial disclosure form.

In a separate matter, it said it will continue to look into Rep. Michele Bachmann (R-Minn.) and two other members facing investigation.

At issue in Tierney's case was money that his wife, Patrice, received from her brother, who was convicted of running an illegal gambling ring. Patrice Tierney pleaded guilty in 2010 to "willful blindness" of the gambling operation and tax fraud.

She received $200,000 from her brother -- money that would have to be reported if it was income, but not if it was considered a "gift," as the Tierneys maintain.

The Ethics Committee, headed by Chairman Mike Conaway (R-Texas) and Linda Sanchez (D-Calif.), said Wednesday that whether the money was payment or a gift depends on her brother's intent, which cannot be surmised by the current evidence.

In addition, family members have more leeway to give each other monetary gifts.

"The Committee reviewed the allegations, conducted additional investigation as necessary, and unanimously concluded that the presently-available evidence was inconclusive as to whether the payments to Mrs. Tierney were income or gifts and does not warrant a finding that Representative Tierney intentionally mischaracterized the nature of the payments for financial disclosure or tax purposes."

The committee continued: "Therefore, after careful consideration, the Committee has unanimously voted to close the matter referred by the OCE, determined that no further action is required at this time, and agreed to end its review of this matter with the publication of this Report..."

The legal saga surrounding Tierney, his wife and his wife's brother made Tierney a top target for Republicans in 2012, and they nearly upended him in a strongly Democratic district.

This year, Tierney faces Iraq veteran Seth Moulton in a primary and a potential rematch with former GOP state Sen. Richard Tisei.

"I thank the Ethics Committee for its unbiased and expedited review," Tierney said in a statement. "After three years of politically motivated, partisan attacks on this issue, I look forward to putting it behind me. "

As for Bachmann, she faces an investigation into potential improper use of leadership PAC funds for her 2012 presidential campagn.

The committee declined to launch a full-scale investigation at this point but said it will continue to review the matter.

In a statement, Bachmann emphasized that she trusted aides to comply with the law.

"As the committee’s statement points out, ‘the mere fact of conducting further review … does not itself indicate that any violation has occurred, or reflect any judgment on behalf of the Committee,’" Bachmann said. "Although I do not believe a referral was warranted, I respect the Committee process and I look forward to a successful conclusion to this matter.”

In two separate matters, investigations into Reps. Tim Bishop (D-N.Y.) and Peter Roskam (D-Ill.) will continue as well.

The four cases were referred to the committee by the Office of Congressional Ethics, a separate panel that looks into the actions of lawmakers.