VACAVILLE, Aug. 13 — Prison officials feared yesterday that someone had sent convicted mass murderer Charles Manson a bomb, but the package contained only a teddy bear toy and a Polish travel book.

The incident began when a checking device at the California Medical Facility registered that the package contained wires. Guards moved the package to a safe area and covered it with sandbags.

Then a specially trained “bomb-sniffing” dog was brought to the prison from Travis Air Force Base. The dog went into what prison authorities termed a “classic alert” position, making them think they had a bomb on their hands.

The five-by-eight-inch package, with a return address in Poland, was carted out to a nearby orchard by the Concord Police Dept. bomb squad, which opened it and found the toy and the Polish book.

Vacaville Police Chief James Lehman said wires inside the teddy bear may have set off the checking device. There was no word on what prompted the dog to go into its “classic alert.”

The 41-year-old Manson, convicted in the 1969 slayings of actress Sharon Tate and six others, was moved from Folsom to Vacaville, 40 miles west of Sacramento, in May to undergo psychiatric study.

Prison authorities had said Manson was “becoming extremely withdrawn” at Folsom.