A teenager is in custody accused of making threats towards Adelaide’s largest public school and two of South Australia’s most popular public events.

The arrest of the 19-year-old, whose identity is under a secrecy order, follows a careful large-scale operation involving both state and federal authorities.

The Australian Federal Police and detectives from South Australia’s major crime branch stormed inside a home on a suburban street yesterday afternoon.

The man was taken into custody before police began a forensic examination of the property that continued throughout today.

Concerned neighbours watched on as police carried out the high-stakes raid.

“I’m a bit shocked. To me this is a safe area,” one resident said.

“I walk past here every day and it’s very quiet, so I never imagined such a thing happening.”

The teenager fronted court this afternoon charged with blackmail and contaminating goods. 

9News heard allegations the teenager had been threatening to build bombs that could kill and had plans for AFL Gather Round and this year’s Adelaide Fringe Festival.

The other alleged target was Glenunga International High School, known as the state’s largest and best performing public school.   

In February, 9News reported on anonymous threats made via email towards the principal.

Police began investigating immediately and worked with the school to ensure there were extra security measures to keep staff and students safe. =

Other alleged threats included the use of suicide vests, the use of a big car to carry out an attack and experimentation with placing lead in food.

It is believed that allegation is linked to the contaminating goods charge, while one of the blackmail charges relates to an alleged demand for $23 million in cash and Bitcoin.

During the first court hearing, the teenager applied for bail but police prosecutors were opposed to his freedom being granted in any form due to the seriousness of the allegations.

Prosecutors told the court the accused was highly skilled with computers and he has been known to hack into computer systems.

Their fear is if he were to be released he may destroy evidence.

The teenager, who appeared in court via video link, did not talk or react during the hearing which lasted about an hour.

His lawyer told the court the man denies the allegations and they will be contesting the charges.

The teenager’s bail was refused and he will remain in custody until at least December.