Police in Austria have questioned three teenagers suspected of plotting a suicide attack at a Taylor Swift show, sparking renewed concerns over the indoctrination of young people online.

Investigators unearthed a stockpile of chemicals, explosive devices and detonators at the home of the main suspect, a 19-year-old ISIS sympathizer who had been radicalized online, according to authorities.

The young man – who was arrested Wednesday morning in the eastern town of Ternitz – planned to kill himself and “a large number of people,” according to the head of the domestic intelligence agency, Omar Haijawi-Pirchner.

“He said he intended to carry out an attack using explosives and knives,” Haijawi-Pirchner told reporters in Vienna on Thursday. “His aim was to kill himself and a large number of people during the concert, either today or tomorrow.”

Two other suspects were detained, aged 17 and 15. The 17-year-old worked for a facilities company that would have provided services at the concert venue. He was near the stadium when he was arrested and had recently broken up with his girlfriend, according to Haijwai-Pirchner.

Little has been revealed about the 15-year-old. Prosecutors will decide later if he was a witness or directly involved in the alleged plot.

The three are all Austrian citizens with either Turkish, North Macedonian or Croatian backgrounds.

The trio were in contact with other individuals who knew about the plan, said the country’s director general for public security, Franz Ruf. No-one else is being sought in direct connection with the plot, Ruf added.

The cancellations of the Swift concert triggered an outpouring of heartbreak, grief and relief among Swifties hoping to attend the record-breaking Eras Tour in Vienna. Hailed as a cultural phenomenon, the scale, influence and intricacy of Swift’s musical voyage have made headlines for boosting the economies of the cities she visits.