The FBI on Wednesday arrested a 66-year-old man in Sacramento on suspicion of mailing 120 hoax anthrax packets, including one to the San Diego Union-Tribune.

Marc Keyser was arrested without incident. No alleged motive was announced.

A packet marked as anthrax arrived at the San Diego newspaper along with a CD with the name Colin Powell scrawled on it. The FBI and San Diego Fire Department shut down the employee entrance to the newspaper.

A field test determined the contents were not anthrax, authorities said. Other packets were sent to media organizations, a congressional office and at least two restaurants, authorities said.

According to the FBI, each of the packages contained a CD titled “Anthrax: Shock & Awe Terror.” Attached to the CD was a sugar packet containing a white powdery substance and a label depicting an orange biohazard symbol and the words “Anthrax Sample.”

Several of the packages were collected and sent to the FBI laboratory in Quantico, Va., for processing. So far, none of the contents have tested positive for biohazardous material, the FBI said.

Authorities said it was likely that many other mailings will be received over the next few days. Recipients of the mailings are advised to contact their local FBI office so that the packages can be collected and preserved as evidence.

Keyser’s arrest was not connected to another series of powder-hoax mailings sent to financial institutions recently, according to the FBI.

Keyser was arrested at his residence without incident and was in custody at the Sacramento County Jail. He is scheduled to appear in federal court Thursday afternoon.

Perry is a Times staff writer.

tony.perry@latimes.com