The committee did not reveal the nature of the complaints, but the offices of the three lawmakers said they are related to campaign spending and not the members’ official congressional duties.
Tlaib is a high-profile freshman Democrat from Detroit, while Huizenga, a Republican, is in his fifth term representing west-central Michigan.
Spano, a Republican, is a freshman from central Florida.
All three lawmakers denied wrongdoing, saying in separate statements that they were cooperating with investigators.
The complaint against Tlaib focused on her decision to pay herself $4,000 a month in salary from her 2018 campaign account, an action that conservative groups called improper.
A spokesman for Tlaib called the complaint politically motivated. Tlaib, part of the “squad” of freshman women of color in the House, is an outspoken critic of President Donald Trump and has been the focus of repeated attacks from Trump and other Republicans.
“Representative Tlaib fully complied with the law and acted in good faith at all times,” said Denzel McCampbell, a spokesman for Tlaib.
Brian Patrick, a spokesman for Huizenga, called the complaint against the congressman “partisan and politically motivated” and said it has been resolved by the Federal Election Commission.
The FEC complaint alleged that Huizenga had misused his campaign account for personal use and had failed to properly itemize expenses. He denied wrongdoing.
Spano, in a statement released by his office, said the ethics panel was reviewing self-reported filings with the FEC. Published reports indicate that Spano borrowed more than $100,000 from two friends and then loaned it to his campaign. He has since repaid the loans, with the proceeds of a bank loan to himself.
“I think this is a step in the right direction as I want to ensure my record of transparency and accountability is publicly highlighted,” Spano said Monday. While he has doubts about the timing and motive behind the inquiry, “I am confident the process will ultimately lean in my favor,” he said.
The ethics panel began the reviews after separate referrals from the independent Office of Congressional Ethics, which investigates complaints against House members.
The ethics panel stressed that the review “does not itself indicate that any violation has occurred, or reflect any judgment on behalf of the committee.”
The panel says it will announce next steps in November.