SANTA ANA. Calif. — The state attorney general’s office is investigating a letter received by some Orange County Hispanic residents that says it is a crime for immigrants to vote and warns them that they could be jailed or deported if they go to the polls next month.

The letter, written in Spanish, also says that the state has developed a computer system that will make it easy to track down the names of Hispanic voters.

“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,” the letter says.

Local officials said the note was degrading and intimidating, and they asked state and federal officials to step in.

“You can’t help but feel disgusted with the contents of this letter. I’m not just going to sit silent,” state Senator Gloria Romero, a Democrat of Los Angeles, who is up for re-election in November, said.

A spokesman for state Attorney General Bill Lockyer, Nathan Barankin, said the letter was “something we are investigating aggressively right now.”

The sender could be charged with a felony and receive up to three years in state prison, he said.

The note’s letterhead resembles that of the California Coalition for Immigration Reform, a Huntington Beach-based group that advocates for stricter border controls, among other things.

The group’s founder, Barbara Coe, said she did not know the person who signed the letter, “Sergio Ramirez,” did not herself authorize it, and was unaware of anyone in her group who did. The letter has a variation of an eagle logo used by the group on its Web site. It doesn’t have the group’s “official” logo, an outline of the state of California.

Ms. Coe said that, in the last four days, she had taken dozens of calls from Orange County Latinos who received the letters.

It “puts a shadow on our credibility, that we would target certain people who might be citizens of our country,” she said.

The FBI investigated Ms. Coe’s group in 1996 and 1998 because members held signs near polls stating only citizens could vote.

Several of the people who received the letters appeared to be naturalized citizens, John Trasvina, said. Mr. Trasvina is interim president and general counsel for the Mexican American Legal Defense and Education Fund. Naturalized citizens can register to vote.

A Garden Grove City Council candidate, Benny Diaz, said his wife received the letter, as well as at least five others with Hispanic surnames he knows.

“It’s a very malicious and degrading letter. It’s to pull Latinos down and make them afraid,” he said.