The federal government has closed a criminal probe of alleged financial misconduct by Arizona lawman Joe Arpaio, who styles himself as "America's toughest sheriff," and no charges will be filed, the U.S. Attorney's Office said on Friday.

A separate federal investigation relating to allegations of civil rights abuses by Arpaio's office is continuing. 

The announcement on Friday marked the end of an investigation that began in November 2010 at the behest of the Maricopa County Board of Supervisors to examine alleged financial improprieties by the county sheriff and his deputies.

A federal criminal inquiry into several of those matters was concluded last summer with the U.S. Attorney's Office in Arizona declining to initiate criminal charges. 

Maricopa County authorities were informed on Friday that federal prosecutors had likewise declined to bring charges in connection with allegations that the sheriff's office had misused county credit cards or misspent money from jail facilities excise taxes.

In addition, the U.S. Attorney's Office declined to prosecute two former officials of the county attorney's office who were accused of wrongfully prosecuting a local judge.

Assistant U.S. Attorney Ann Birmingham Scheel said in a statement that her office "is closing its investigation into allegations of criminal conduct by current and former members of the Maricopa County Sheriff's Office and the Maricopa County Attorney's Office."

Arpaio, who returned from the Republican National Convention on Friday night, said he was "very happy" with decision.

"I send my appreciation to the federal government for their hard work in clearing my office," he said in a news briefing. 

Arpaio, 80, who is seeking re-election to a sixth term as sheriff in November, has been under a separate federal inquiry since 2008 over allegations that he and his deputies engaged in an extensive pattern of civil rights abuses.

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Arpaio denied any wrongdoing, and said he would cooperate with investigators.

Assistant U.S. Attorney Ann Birmingham Scheel, acting on behalf of the United States due to the recusal of U.S. Attorney John S. Leonardo, commended the joint investigative efforts of the prosecutors and the FBI special agents who conducted the investigation.

Scheel said her office advised Maricopa County Attorney Bill Montgomery of the decision.

Arpaio, first voted into office in 1992, has been elected five times and is seeking a sixth term.

In July, Arpaio said that volunteer investigators working for him concluded that President Barack Obama’s birth certificate is not legitimate.

"At the very least," he said at a news conference, "I can tell you this, based on all of the evidence presented and investigated, I cannot in good faith report to you that these documents are authentic."

Also in July, Arpaio denied in testimony in a class-action lawsuit that his deputies targeted people because of the color of their skin.

He was testifying whether police can target illegal immigrants without racially profiling Hispanic citizens and legal residents.

"I am against anyone racial profiling ... today as in my 50 years in law enforcement," Arpaio told the court during cross-examination. 

Arpaio is also known for outfitting county jail inmates in pink underwear, claiming the pink shorts are less likely to be smuggled out of jail and sold on the black market, and for housing inmates in a Tent City jail in Phoenix, even when Sonoran Desert summer temperatures soar to 115 degrees.

NBC's Jim Gold and Reuters contributed to this report.

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