VALLEJO, Calif. (AP) _ A threatening letter from someone claiming to be the Zodiac Killer was delivered to a newspaper Wednesday, the first such communication in 13 years from the man blamed for five deaths, authorities said.

''He says he's going to run over little kiddies at Halloween,'' said Jim Jones, general manager of the Vallejo Time-Herald.

''I'm sure that probably by tomorrow early, we'll know if it's authentic,'' Vallejo Police Lt. Gerald Greenhouse said Wednesday.

Greehouse said the letter was delivered to the Vallejo Times-Herald newspaper, two months shy of the 19th anniversary of Zodiac's first known Northern California killing.

The Zodiac began sending letters to the Times-Herald after the Dec. 20, 1968, shootings of two people in northeast Vallejo. After sending several more to the paper, he began sending them to the San Francisco Chronicle, most in codes.

Police say at least five people are believed to have been slain by the Zodiac, although he claimed many more victims in his bizarre, often rambling letters.

The Zodiac would write notes, often threatening to kill, in a cryptogram composed of letters and signs that initially baffled professional code breakers.

The letters were signed with a circle divided by a cross. Subsequent letters began, ''This is the Zodiac speaking.''

His last authenticated letter to the Chronicle arrived Jan. 30, 1974. His identity is still a mystery.

Greenhouse would not disclose the contents of the letter.

''Because of the threats contained in the letter, we are expediting making a determination as to the authenticity of the letter with the assistance of the Department of Justice in Sacramento,'' he said.

''If the letter appears to be authentic, appropriate plans will be immediately developed to deal with the threats,'' Greenhouse said.