Japhia Huhndorf was arrested at her home in Atwater on suspicion of possessing an explosive device. Police took her to her classroom at Livingston High School, where she cooperated with detectives to find a small amount of nitroglycerin, said Livingston police Sgt. Ray Fong.
Nitroglycerin is used as an active ingredient in the manufacture of explosives, especially dynamite.
Huhndorf, 34, had been out on bail after she was arrested earlier this week on suspicion of child endangerment. Authorities had accused her of helping three students at the school inhale chloroform during after-school study hall sessions.
Fong said the three male students - ages 16, 17 and 18 - told investigators that they fell asleep or passed out after ingesting the chloroform, an anesthetic that can cause feelings of euphoria but in high levels can cause unconsciousness or even death.
Police re-arrested Huhndorf after interviewing her and the students and finding documents in her classroom showing she might be storing explosive materials, Fong said. The teens are not involved with the explosive material, he said.
When the nitroglycerin was found at about 2 p.m., about 1,100 students were evacuated for the day and a hazardous material team and bomb squad were sent into the school, about 60 miles east of San Jose.
Investigators detonated the material in a field behind the school, Fong said. He said investigators did not know why Huhndorf had the nitroglycerine.
School officials did not want to comment on the investigation. Fong said school would be back in session Thursday.
Huhndorf could not be reached for comment. A woman who answered the phone earlier Wednesday at a home number listed for Huhndorf said she didn't know the teacher.