The investigation was opened in the final months of the Trump administration under Attorney General William P. Barr, the two people said. Given Mr. Gaetz’s national profile, senior Justice Department officials in Washington — including some appointed by Mr. Trump — were notified of the investigation, the people said.
The three people said that the examination of Mr. Gaetz, 38, is part of a broader investigation into a political ally of his, a local official in Florida named Joel Greenberg, who was indicted last summer on an array of charges, including sex trafficking of a child and financially supporting people in exchange for sex, at least one of whom was an underage girl.
Mr. Greenberg, who has since resigned his post as tax collector in Seminole County, north of Orlando, visited the White House with Mr. Gaetz in 2019, according to a photograph that Mr. Greenberg posted on Twitter.
No charges have been brought against Mr. Gaetz, and the extent of his criminal exposure is unclear.