Donald Trump's administration has ordered the resignations of 46 US attorneys who were appointed by Barack Obama.
Many of the federal prosecutors have already left their positions, but those who stayed on have been asked to leave by attorney general Jeff Sessions "in order to ensure a uniform transition".
A Justice Department spokeswoman said: "Until the new US attorneys are confirmed, the dedicated career prosecutors in our US attorney's offices will continue the great work of the department in investigating, prosecuting and deterring the most violent offenders."
It is customary, though not automatic, for the country's 93 US attorneys to leave their positions once a new president is in office.
The Obama administration allowed political appointees of President George W Bush to serve until their replacement had been nominated and confirmed.
The federal prosecutors are nominated by the president, generally on the recommendation of a senator.
One US attorney appointed by Bush, Rod Rosenstein of Maryland, remained in the job for the entire Obama administration and is the current nominee for deputy attorney general.
US attorneys are responsible for prosecuting federal crimes in the territories they oversee.
They report to Justice Department leaders in Washington and their priorities are expected to be in line with those of the attorney general.