The Justice Department sued Joe Arpaio, sheriff of Arizona's Maricopa County, on Thursday, saying his office has repeatedly declined to hand over documents to federal investigators examining whether his aggressive tactics against illegal immigrants have violated their civil rights.

Arpaio, whose Phoenix area office has drawn widespread attention for his unusual practices, has been the focus of U.S. investigators who have opened criminal and civil investigations of the sheriff and his office.

Justice officials said that Arpaio's decision not to respond to routine document requests was rare, and that he had produced few of the documents sought.

"The actions of the sheriff's office are unprecedented," said Thomas E. Perez, assistant attorney general for the civil rights division. "It is unfortunate that the department was forced to resort to litigation to gain access to public documents and facilities."

In a statement, Arpaio and his attorney suggested that the lawsuit is a publicity stunt. They said that the sheriff's office had turned over "thousands of pages" of documents and that it pledged as recently as this week to cooperate with federal authorities.

"These actions make it abundantly clear that Arizona, including the Sheriff, is Washington's new whipping boy," Arpaio said. "It's time to take the gloves off."

The lawsuit is the third filed by the Justice Department in connection with how authorities in Arizona handle immigrants. On Monday, the department sued a network of community colleges in Maricopa County, saying they placed illegal requirements on non-citizens seeking jobs. In May, the department sued the state and Gov. Jan Brewer (R) over the state's new immigration law.

A federal grand jury in Phoenix is examining whether Arpaio misappropriated federal money and used his office to intimidate his political opponents. The Justice Department's civil rights division is investigating whether Arpaio's office engaged in "discriminatory police practices and unconstitutional searches and seizures," and whether his jail discriminated against Hispanic inmates, according to letters the division sent to Arpaio.

The latest lawsuit, filed in federal district court in Phoenix, asks a federal judge to force the sheriff's office to comply with 51 requests for documents and to provide investigators access to jails, command staff, officers and inmates.

In the suit, Justice Department lawyers detail more than a year's worth of letters and meetings between the department and the sheriff's office. While Arpaio initially produced 11 pages of documents, he later held a news conference and sent letters announcing that he would no longer cooperate, the suit says.