Bomb-making materials were found in the home of one of two people suspected of planning a terror attack on upcoming Taylor Swift concerts in Vienna, authorities said Thursday. Both suspects appeared to be inspired by the Islamic State group and al-Qaeda.

The main suspect, a 19-year-old Austrian citizen, fully confessed to the attack plans during an interrogation, according to Omar Haijawi-Pirchner, head of Austria’s Directorate of State Security and Intelligence.

The suspect was “clearly radicalized in the direction of the Islamic State” and allegedly intended to kill himself and “as many people as possible” outside the concert venue using knives and homemade explosives, Haijawi-Pirchner said at a news conference Thursday.

The 19-year-old, who was from the Austrian town of Ternitz and had North Macedonian roots, had been preparing for the attack since late July and drastically changed his appearance, according to Franz Ruf, the public security director at Austria’s Ministry of Interior. The 19-year-old researched bomb-making techniques and uploaded an oath of allegiance to the current leader of the Islamic State, Haijawi-Pirchner said.

A second suspect, a 17-year-old Austrian citizen, was arrested in Vienna on Wednesday afternoon. A 15-year-old Turkish citizen was also detained and questioned, according to Haijawi-Pirchner. No further suspects are being sought, Ruf said.

Each of the two suspects was known to police, and both were said to have been involved in the direct preparation of the foiled attack, according to Haijawi-Pirchner. Most of the plans and preparations were made at the 19-year-old’s home, Ruf said.

The 15-year-old, who was interrogated, had been asked by the main suspect about ignition mechanisms, Haijawi-Pirchner said.

The 17-year-old suspect, who has Turkish-Croatian roots, was employed a few days ago at a facility company providing services at the concert venue and would have been working there, according to Haijawi-Pirchner. It was discovered during the investigation that he was on the grounds of Vienna’s Ernst Happel Stadium, where Swift’s concerts were to be held.

Swift had concerts scheduled for Thursday, Friday, and Saturday in Vienna.

When Ruf announced the arrests on Wednesday, he said security at the shows would be increased. Hours later, the concerts were canceled.

“We have no choice but to cancel the three scheduled shows for everyone’s safety,” a message from Barracuda Music said. “All tickets will be automatically refunded.”

The Vienna shows were expected to draw 65,000 concertgoers per day, with an additional 10,000 to 15,000 fans outside of the area, police said.

One of those fans planning to attend a Vienna show, Joelle Ferri, told ABC News that, despite the cancellation, Swifties have gathered to sing songs and make friends.

“There are so many Swifties everywhere trading bracelets, wearing merch, and the outfits they were going to wear for the concert,” Ferri said. “This is genuinely the most beautiful thing I have experienced, seeing everyone come together after such a horrible thing happened, and everyone kept their head high and made it a good experience for everyone.”

Another would-be concertgoer, Colleen Boltz, told ABC News she was at the airport in Minneapolis, en route to Vienna, when she learned the show was canceled.

“We still plan on going to Vienna and participating in the Swiftie gatherings. I’m meeting up with Swifties that I met online, and it will still be a blast,” she said.

Boltz also has a ticket to one of Swift’s upcoming London shows. The pop star is set to return to London’s Wembley Stadium from Aug. 15 to Aug. 20.

“We really hope that she does not need to cancel London,” Boltz said.