State investigators have linked a Republican campaign to letters sent to thousands of Orange County Hispanics warning them that they could go to jail or be deported if they vote next month, a spokesman for the attorney general said.

“We have identified where we believe the mailing list was obtained,” a spokesman for Attorney General Bill Lockyer, Nathan Barankin, said.

He declined to identify the specific Republican campaign Wednesday, citing the ongoing investigation. The Los Angeles Times and the Orange County Register both reported yesterday that the investigation appeared to be focused on the campaign of Tan Nguyen, who is a Republican challenger to Rep. Loretta Sanchez, a Democrat.

The letter, written in Spanish, tells recipients: “You are advised that if your residence in this country is illegal or you are an immigrant, voting in a federal election is a crime that could result in jail time.”

Immigrants who are naturalized Americans citizens can vote.

Complaints about the letters this week prompted state and federal investigations, and Mr. Barankin said investigators had been questioning people in Orange County.

The two newspapers reported state investigators had found the location where the letters were printed and mailed to an estimated 14,000 Democratic voters in central Orange County. The Los Angeles Times, citing an unnamed source, said authorities had interviewed Mr. Nguyen at his office.

Mr. Nguyen did not return messages left by the Associated Press or either newspaper.

Ms. Sanchez said in an interview yesterday on Univision that the sender should be punished for stating that immigrants can’t vote. It would be unfortunate if the person responsible was another immigrant, she said.

“What a shame, really, that this is still happening in the United States today,” Ms. Sanchez said.

The owner of Huntington Beach-based Mailing Pros, Christopher West, told the Orange County Register that he was hired to do the mailings but didn’t know what they said and didn’t know any laws were being broken when the mailer was sent. He said he gave investigators the name of the person who hired him.

“I’m the one that processed it, and I don’t read Spanish,”Mr. West said.”Until the investigator read it to me, I didn’t know the content.”

A chairman of the Orange County Republican Party, Scott Baugh, condemned the letter as “an obnoxious, grotesque piece of work.”

“Regardless of who did it — Republican or Democrat — if it’s a crime, then whoever did it should be prosecuted,” Mr. Baugh said.