LOS ANGELES, Oct. 30 (Xinhua) -- A Californian man suspected of sending more than 120 anthrax hoax letters to news media across the United States this week had been warned by law enforcement that such actions were illegal, court documents showed Thursday.

    Marc Keyser was arrested late Wednesday by FBI agents at his home in the state capital city of Sacramento on charges of sending a hoax letter.

    The FBI said the 66-year-old AIDS and education activist sent more than 120 envelopes containing a CD labeled as "Anthrax Sample" with an orange biohazard symbol attached. All the letters have been so far tested as non-dangerous.

    Among those who received the letters by Wednesday were two Sacramento TV stations, the San Diego Union-Tribune newspaper, a newspaper in North Carolina and the office of Republican Congressman George Radanovich in California.

    A criminal complaint filed in U.S. District Court in Sacramento Thursday states that Keyser was questioned about two years ago by FBI agents for sending a package marked "anthrax" to a local news organization and warned that such actions were illegal.

    Keyser was not arrested in the 2007 case. When the new packages began appearing at media and other outlets across the country this week, FBI agents returned to his home Wednesday and he admitted that he had sent the packages.

    Keyser was arrested Wednesday and faces three counts in connection with the mailings.