Till was abducted from his uncle's home in Money, Miss., on Aug. 28, 1955. The mutilated body of the 14-year-old from Chicago was found by fishermen three days later in the Tallahatchie River.
Pictures of the slaying shocked the world. Two white men charged with murder — Roy Bryant and his half brother, J.W. Milam — were acquitted by an all-white jury. Both men have since died.
According to the Justice Department, the men "subsequently detailed to a magazine journalist how they beat Till, took him to the river, shot him in the head, tied a large metal fan to his neck with barbed wire, and pushed his body into the river."
Justice Department officials did not say what prompted them to reopen the case. Details of the renewed investigation, which also involves officials in Mississippi, were announced Monday by R. Alexander Acosta, assistant attorney general for civil rights.
"Recent renewed interest in the matter has suggested the potential that others were involved in the murder," a department statement read.
The federal statute of limitations in the case expired long ago, but state prosecution is still possible, the Justice Department says, so federal investigators will work with state counterparts to determine if charges are warranted.
"The Emmett Till case stands at the heart of the American civil rights movement," said Acosta. "This brutal murder and grotesque miscarriage of justice outraged a nation and helped galvanize support for the modern American civil rights movement."
"Even if it's incredibly difficult, we … you know, it's an appropriate use of department resources to investigate matters such as this, Acosta said. "We owe it to them and to the civil rights movement to look into it if an investigation may uncover evidence of additional actors."
The Till murder was immortalized in a 1963 Bob Dylan song "The Death of Emmett Till," which called the trial of Byrant and Milam "a mockery."
The NAACP and other individuals and groups have called repeatedly for reopening the case, which has been the subject of documentary films and books. In a 2003 letter to Mississippi officials, NAACP President Kweisi Mfume said it was "time to address what remains an ugly mark" in state and U.S. history.
Other civil rights-era killings in Mississippi have been reopened with mixed results.
In 1994, Byron de la Beckwith was convicted of the 1963 murder of NAACP field secretary Medgar Evers. But there has been little progress in an effort to bring murder charges for the 1964 slayings of three civil rights workers in Neshoba County, Miss. Those killings were chronicled in the film "Mississippi Burning."