CARLSBAD, Calif. -- A Carlsbad teen who died on an outing to Joshua Tree National Park had consumed a hallucinogenic tea made from jimson weed, but toxicology tests did not show whether the dose was fatal.

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Eric Sears' body was too decomposed for pathologist to determine if the dose was fatal, according to Dr. Manuel Montez of the Riverside County Sheriff-Coroner's Office.

Jimson weed, a member of the Datura, or nightshade family, is considered highly poisonous.

The investigation into the death Sears, 17, will be closed, with the cause of death listed as "undetermined," Montez said.

"There is not sufficient evidence to suggest criminal activity resulted in the death of Eric Sears," Montez said in the toxicology report.

Sears was reported missing July 15 by his friend. Searchers found Sears' body July 23 less than two miles from the boys' campsite.

His friend told authorities that he and Sears drank tea made from jimson weed the night before the disappearance. The plant grows wild and is not illegal.

Early in the investigation, police suspected foul play in the death, but investigators found no signs of trauma to Sears' body.