The office of the United States attorney in Manhattan announced on Thursday that it was joining the investigation into the death of Samuel Harrell, a prisoner at the Fishkill Correctional Facility in Beacon, N.Y., who inmate witnesses say was handcuffed and beaten severely this year by a group of corrections officers.

In a brief statement, the United States attorney for the Southern District, Preet Bharara, said that his office would be “coordinating and working” with the Dutchess County district attorney’s office, which is also investigating the case.

Citing the accounts of 19 inmate witnesses, The New York Times reported last week that Mr. Harrell, who was 30, died on April 21 after an encounter with as many as 20 corrections officers, including a group known around the prison as the Beat Up Squad. The inmates described corrections officers repeatedly punching and kicking Mr. Harrell, who was black, while shouting racial slurs. They said that after he was beaten, officers either threw or dragged him down the stairs.

The officers told an ambulance crew that Mr. Harrell had likely had a drug overdose, but an autopsy report obtained by The Times showed that Mr. Harrell had no illicit drugs in his system. The autopsy, which was conducted by the medical examiner in neighboring Orange County, classified the death as a homicide.

“The very nature of this case calls for a full, fair and objective investigation into not only potential criminal law violations, but constitutional violations as well,” William V. Grady, the Dutchess County district attorney, said in a news release.

Despite repeated requests by The Times, the State Department of Corrections and Community Supervision has provided only minimal details about Mr. Harrell’s death. The corrections department and the State Police said on Thursday that they would work with prosecutors as they review the case.

Building 21 of the Fishkill prison, where Mr. Harrell died, has long been identified by inmate advocates as a violent place where corrections officers routinely abused prisoners. This month, the superintendent at Fishkill, William J. Connolly, abruptly resigned. Officials from the corrections department said this week that his successor has been directed to investigate problems at Building 21 and neighboring 21A.

Mr. Bharara’s decision to join the investigation comes at a time when the corrections department is already under enormous scrutiny. In June, two convicted murderers escaped from the Clinton Correctional Facility in Dannemora, N.Y., leading to a costly three-week manhunt. A civilian prison employee has pleaded guilty to aiding in the escape; a corrections officer has been criminally charged; nine other officers were suspended; and the prison’s leadership team was removed.

Though no inmate has been implicated, dozens later described being abused by guards in the hours and days after the escape, some complaining of being punched, choked with plastic bags and threatened with waterboarding.

For years, Mr. Bharara’s office has aggressively pursued cases involving allegations of civil rights abuses against inmates by guards. In June, his office settled a class-action lawsuit over widespread abuse of inmates at Rikers Island, reaching an agreement with New York City on a host of changes, including the appointment of a federal monitor to oversee the city’s jails.

Mr. Grady said he has been discussing “a joint investigation” with Mr. Bharara’s office for several days. “We will coordinate and work closely to conduct a thorough investigation of this matter, utilizing the full investigative resources of both the federal and state governments.”