WASHINGTON, July 20 — A report by internal investigators at the Justice Department has identified dozens of recent cases in which department employees have been accused of serious civil rights and civil liberties violations involving enforcement of the sweeping federal antiterrorism law known as the USA Patriot Act.

The inspector general's report, which was presented to Congress last week and is awaiting public release, is likely to raise new concern among lawmakers about whether the Justice Department can police itself when its employees are accused of violating the rights of Muslim and Arab immigrants and others swept up in terrorism investigations under the 2001 law.

The report said that in the six-month period that ended on June 15, the inspector general's office had received 34 complaints of civil rights and civil liberties violations by department employees that it considered credible, including accusations that Muslim and Arab immigrants in federal detention centers had been beaten.

The accused workers are employed in several of the agencies that make up the Justice Department, with most of them assigned to the Bureau of Prisons, which oversees federal penitentiaries and detention centers.

The report said that credible accusations were also made against employees of the F.B.I., the Drug Enforcement Administration and the Immigration and Naturalization Service; most of the immigration agency was consolidated earlier this year into the Department of Homeland Security.

… While most of the accusations in the report are still under investigation, the report said a handful had been substantiated, including those against a federal prison doctor who was reprimanded after reportedly telling an inmate during a physical examination that "if I was in charge, I would execute every one of you" because of "the crimes you all did."

…The report said that the inspector general's office was continuing to investigate a separate case in which about 20 inmates at a federal detention center, which was not identified, had recently accused a corrections officer of abusive behavior, including ordering a Muslim inmate to remove his shirt "so the officer could use it to shine his shoes."