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Six Miami firefighters have been fired after an investigation found they hung a noose on a black colleague's family photo.

Photos of the firefighter's children and mother were also defaced with lewd doodles in the 9 September incident.

The dismissals came on Wednesday after police interviewed 20 people at the fire station, according to US media.

Miami City Manager Daniel Alfonso said investigators found "sexually explicit and racially offensive conduct".

"We cannot and will not tolerate behaviour that is disrespectful, hurtful and compromises the integrity of the department and the City of Miami," Mr Alfonso said in a statement following the police investigation.

The noose is considered offensive in the US because of extrajudicial executions, predominantly of black men, that became a common public spectacle in the South after the American Civil War.

Media playback is unsupported on your device Media caption Racism in the US: Is there a single step that can bring equality?

Sources tell the Miami Herald that the noose was tied from twine, and draped over an African-American lieutenant's family photo.

Termination letters sent on Wednesday told the firefighters: "You engaged in conduct unbecoming of a firefighter when you participated in defacing several personal photos of a fellow firefighter with graphic and obscene phallic renderings."

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Firefighters Kevin Meizoso, David Rivera, Justin Rumbaugh, Harold Santana and Alejandro Sese were fired, as well as William Bryson - the son of a former fire chief.

Under their contracts, they firefighters can challenge their terminations.

In the nearby city of Pompano Beach, Florida, four firefighter recruits were dismissed in August following a similar incident, in which a noose was hung over the desk of a black recruit.

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