Reporting from Denver - A federal grand jury is investigating Joe Arpaio, the Arizona sheriff known for his aggressive stance on illegal immigration, for possible abuses of power in launching investigations of local officials who disagree with him, authorities said Friday.

Two Maricopa County officials have been subpoenaed to appear before the grand jury to testify about Arpaio's actions against county officials since they moved to cut his budget in late 2008.

Since then Arpaio and County Atty. Andrew Thomas, an ally, have filed criminal charges against two county supervisors, have said dozens of other county workers are under investigation and have filed a federal racketeering lawsuit accusing the entire county political structure of conspiring against them.

The investigation of Arpaio has been rumored for months, but the statements from County Manager David Smith and Deputy County Manager Sandi Wilson confirming the subpoenas, issued Thursday, are the first official confirmation.

The FBI and U.S. attorney's office in Phoenix declined to comment on the investigation. Arpaio's office did not return a call for comment.

In an interview Friday, Wilson, the county's budget chief, said a prosecutor from the U.S. attorney's office met with her and Smith this week. "They told us that they were looking at abuses by Sheriff Joe Arpaio and his office, abuses of power," she said.

Wilson said she was not asked about the sheriff's controversial immigration policies. Arpaio uses his deputies to enforce federal immigration law and is known for sending hundreds of officers into heavily Latino neighborhoods to ask anyone who commits violations as minor as jaywalking about their immigration status.

Among the officials targeted by Arpaio and Thomas has been Supervisor Mary Rose Wilcox, the lone Democrat on the board, for possible conflict of interest.

Wilson, whom Arpaio has named as part of a possible criminal conspiracy, said it was a relief that the federal government had looked into complaints from a wide array of Arizona officials about the sheriff's behavior.

"My children are adopted from other countries, and I used to feel good about having brought them here, but now I'm not sure," she said. "It doesn't feel like America here in Maricopa County. You have no idea what it's like to know you could be arrested for just doing your job."

icholas.riccardi@latimes.com