The F.B.I. closed an investigation into a prominent donor and ally of Senator Susan Collins last year. Senior bureau officials questioned the credibility of the donor’s account, according to current and former officials.
The inquiry had examined whether the donor’s actions violated federal law. It is unclear what specific allegations prompted the investigation or when it formally began.
Officials said the decision to shut down the case came after internal reviews raised doubts about the donor’s statements. No charges were filed, and the matter was not referred for prosecution.
The donor has been a longtime supporter of Collins, contributing to her campaigns and attending high-profile events. The relationship has drawn scrutiny in the past but never resulted in legal action.
Collins’s office did not comment on the closed inquiry. The senator has previously defended her connections to donors, saying they do not influence her legislative decisions.
The F.B.I. declined to confirm or deny the investigation. Spokespeople for the bureau said they do not discuss closed cases unless charges are filed.
Legal experts say closing an inquiry based on credibility concerns is common. Prosecutors often drop cases when witness accounts are inconsistent or unverifiable.
