The Justice Department has added two top prosecutors from Washington to the child sex trafficking investigation of Representative Matt Gaetz, according to two people briefed on the matter, a sign of the complex and high-stakes nature of the inquiry into Mr. Gaetz, a Florida Republican who is one of former President Donald J. Trump’s closest congressional allies.

The prosecutors — one a public corruption investigator with an expertise in child exploitation crimes, and the other a top leader of the public corruption unit — have been working on the Florida-based investigation for at least three months, the people said.

It is not unusual for prosecutors from the Justice Department in Washington to be added to local teams of federal investigators in high-profile cases that require a deep and specific expertise like sex crimes…

One of the questions the prosecutors will have to wrestle with is whether to charge Mr. Gaetz with the same crime that Mr. Greenberg pleaded guilty to, sex trafficking a minor. The law is broadly written and carries a minimum mandatory sentence of 10 years in prison.