By Tim Gaynor
PHOENIX (Reuters) - A hard-line Arizona sheriff under federal investigation for alleged racial profiling of Hispanics placed parts of a Phoenix jail on indefinite lockdown on Tuesday over what he said were rising racial tensions between Latino and black detainees.
Maricopa County Sheriff Joe Arpaio said tensions at the jail's maximum security unit rose after the Mexican Mafia prison gang urged Hispanic inmates to refuse to be housed with black prisoners, and encouraged fights between them.
Arpaio, who famously makes jail inmates wear pink underwear, took the decision to put the unit on lockdown to protect staff and prisoners after a fight involving 25 Hispanic and black inmates broke out on Monday, his office said. No serious injuries were reported.
"Super max Mexican Mafia inmates housed in the closed custody unit of the 4th Avenue jail are putting out orders to all Hispanic inmates to refuse to be housed with black inmates," the office said in a statement. The statement did not explain a motive for the gang's actions.
The lockdown comes amid heightened sensitivities in Arizona's Latino community surrounding the state's controversial immigration crackdown, as the U.S. Supreme Court prepares to hear arguments on Wednesday over the partially blocked law.
The law, signed by Republican Governor Jan Brewer in 2010, requires police to check the immigration status of people they stop and suspect of being in the country illegally. It was among measures blocked by a federal judge before it took effect.
The part of the Arizona jail on lockdown -- the maximum security unit at the 4th Avenue Jail in Phoenix -- has beds for 288 high-risk prisoners.
Sheriff's intelligence officers also monitored conversations by Mexican Mafia members who the agency said were ordering "racial beat downs on all black inmates." It said detention staff had also been threatened.
The Mexican Mafia, also known as "La eMe" for the Spanish letter M, was formed in the California prison system in the 1950s and is now active in the detention system in more than a dozen U.S. states.
Arpaio, who styles himself as "America's toughest sheriff," is known for controversial sweeps cracking down on illegal immigrants in the Mexico border state. Earlier this month the Obama administration said it was preparing to sue him and his department for violating civil rights laws by improperly targeting Latinos.
Justice Department spokeswoman Xochitl Hinojosa declined to comment on the lockdown on Tuesday.
The sheriff has denied any wrongdoing and lashed out at the Obama administration for targeting his department and failing to handle the issue of illegal immigration to his satisfaction, with more than 11 million illegal immigrants believed to be in the United States.
Arpaio has also been under fire for his treatment of prisoners in his jails. Last month, a federal appeals court noted that a requirement that jail inmates wear pink underwear may be unconstitutional when applied to prisoners who have not been convicted of a crime.
The U.S. 9th Circuit Court of Appeals took up the pink-underwear policy in reinstating a lawsuit against Arpaio and Maricopa County by the estate of a mentally ill man who died of an acute cardiac arrhythmia in 2001, weeks after being forcibly dressed in the underwear by jail officers.
(Additional reporting by Jeremy Pelofsky in Washington; Editing by Cynthia Osterman)