A federal investigation of a controversial Arizona sheriff known for tough immigration enforcement has intensified in recent days, escalating the conflict between the Obama administration and officials in the border state.

Justice Department officials in Washington have issued a rare threat to sue Maricopa County Sheriff Joe Arpaio if he does not cooperate with their investigation of whether he discriminates against Hispanics. The civil rights inquiry is one of two that target the man who calls himself "America's toughest sheriff." A federal grand jury in Phoenix is examining whether Arpaio has used his power to investigate and intimidate political opponents and whether his office misappropriated government money, sources said.

The standoff comes just weeks after the Justice Department sued Arizona and Gov. Jan Brewer (R) because of the state's new immigration law, heightening tensions over the issue ahead of November's midterm elections. The renewed debate has focused attention on Arpaio, a former D.C. police officer who runs a 3,800-employee department, and a state at the epicenter of the controversy over the nation's estimated 12 million illegal immigrants.

http://www.washingtonpost.com/wp-dyn/content/article/2010/08/17/AR2010081703637_pf.html