RIVERSIDE, Calif. (AP) _ Authorities trying to determine if an 83-year-old woman was dead when her head was removed and frozen for possible future revival questioned six people and searched a lab but failed to find the head.

''No one is saying where the head is being kept,'' Riverside County Deputy Coroner Mike Oare said today.

The coroner's office launched an investigation of the Dec. 11 death of Dora Kent when officials learned her head was removed at the Alcor Life Extension Foundation lab without a doctor present to pronounce her dead.

Alcor practices cryonics, the practice of freezing human remains in hopes medical technology will someday advance to the point they can be revived.

The six people arrested, including the president of Alcor, were questioned at the Riverside police station Thursday and later released, said Dan Cupido, a supervising deputy coroner.

Alcor officials refused to disclose where the head was being stored, said Scott Hill, chief deputy coroner.

''The head is gone,'' Cupido said Thursday. ''They took the head.''

Coroner's deputies seized documents, videotapes, charts and slides during the search. A cache of weapons and explosives, including hand grenades, also was found at the facility, Cupido said.

It appeared the people at the cryonics facility were packing files for shipment, Cupido said. ''So there is some suspicion they were getting ready to move,'' he said.

The woman's son, Saul Kent, 48, a member of Alcor, said he chose to have her head frozen because she had severe arthritis and he hoped the rest of her body could be replaced someday.

Mrs. Kent was terminally ill, suffering from a degenerative brain disease, and an autopsy determined she had pneumonia when she died. The question is whether the woman was clinically dead when her head was removed.

Alcor has stored six other frozen heads and one full body at the facility located about 55 miles east of downtown Los Angeles, Cupido said.