PHOENIX –  Federal authorities said Friday that they're closing their abuse-of-power investigation into a sheriff in Arizona without filing charges against him.

Authorities were investigating America's self-proclaimed toughest sheriff, Maricopa County Sheriff Joe Arpaio, for his part in failed public corruption cases against officials who were odds with him. Arpaio brought cases against a judge and two county officials in 2009.

Assistant U.S. Attorney Ann Birmingham Scheel released a statement saying her office "is closing its investigation into allegations of criminal conduct" by current and former members of the sheriff's and county attorney's offices.

Scheel, who is based in Arizona, didn't elaborate but said she was acting on behalf of the U.S. Department of Justice.

The federal probe focused specifically on the sheriff's anti-public-corruption squad. In a separate probe, the U.S. Justice Department has accused Arpaio's office of a wide range of civil rights violations, and in another case, a federal judge has yet to rule in a civil case brought by a group of Latino plaintiffs that claimed Arpaio and his deputies engaged in racial profiling.

Arpaio was scheduled to give a news conference Friday night after returning from the Republican National Convention in Florida.

His deputy chief Jack MacIntyre, said, "the U.S. attorney's office and its investigators recognized what sheriff's office has said all along: We did not make any prosecutorial decisions, even though things were referred to the then-county attorney."

The timing of the federal authorities' announcement -- at 5 p.m. on a Friday before a holiday weekend -- was questioned by some Arpaio critics.

"It is a miscarriage of justice that the federal government is dropping its case against Sheriff Arpaio and to make such an announcement on the Friday night before the Democratic National Convention can only be politically motivated to shield the administration from criticism," Pablo Alvarado, director of the National Day Laborer Organizing Network, said in a statement.


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