A 39-year-old woman was arrested Thursday after authorities say she sent three threatening letters to a Glendora high school.
Magaly Esmeralda Alvarenga was arrested on suspicion of making criminal threats toward St. Lucy's Priory High School, said Glendora Police Sgt. Shawna Celello. The letters were sent between January and last week.
Police would not say what the woman wrote or how they identified her, but did say the threats were not directed at an individual. It's unclear whether Alvarenga has a connection to the school.
"The arrest came as a result of an active and rigorous investigation by our department's detective bureau with the support and cooperation of St. Lucy's Priory High School principal, faculty, staff and students," the Police Department said in a statement.
Alvarenga, who lives in Rialto, is being held on $700,000 bail.