VIENNA (AP) — Both suspects in a foiled plot to attack Taylor Swift shows in Vienna appeared to be inspired by the Islamic State group and al-Qaida, Austrian authorities said Thursday, and investigators found bomb-making materials at one of their homes. Officials said one of the two confessed to planning to “kill as many people as possible outside the concert venue.”

Three sold-out concerts were canceled a day earlier because of the plot, devastating Swifties from across the globe. Many of them had dropped thousands of euros (dollars) on travel and lodging in Austria’s expensive capital city to attend the Eras Tour shows at the Ernst Happel Stadium, which sat empty Thursday morning as media filmed outside.

Concert organizers said they stood behind their decision, saying they expected up to 65,000 fans inside the stadium at each concert and as many as 30,000 onlookers outside, where authorities said the suspects planned to strike.

Officials told reporters that the main suspect, a 19-year-old Austrian, began working on his attack plans in July, and just a few weeks ago uploaded to the internet an oath of allegiance to the current leader of the Islamic State group militia. He planned to use knives or homemade explosives.

“He wanted to carry out an attack in the area outside the stadium, killing as many people as possible using the knives or even using the explosive devices he had made,” said Omar Haijawi-Pirchner, the head of the Directorate of State Security and Intelligence, citing the 19-year-old’s confession.

He was “clearly radicalized in the direction of the Islamic State and thinks it is right to kill infidels,” Haijawi-Pirchner added.

The foiled attack was planned for Thursday or Friday, according to Austria’s interior minister, Gerhard Karner. Neither suspect appeared to have a ticket to any of the shows.

During a raid of the main suspect’s home in Ternitz, south of Vienna, investigators found chemical substances and technical devices that indicated “concrete preparatory acts,” said Franz Ruf, Director General for Public Security at the Ministry of the Interior.

Authorities also found Islamic State group and al-Qaida material at the home of the second suspect, a 17-year-old Austrian. He was employed a few days ago by a company providing services at the venue for the concerts, and was arrested by special police forces near the stadium.

Both teens were arrested Tuesday. Neither’s name was released in line with Austrian privacy rules.

No other suspects are being sought, Karner, the interior minister, said. However, a 15-year-old, who had been in contact with both suspects, was also interrogated by police.

“The situation was serious, the situation is serious. But we can also say: A tragedy was prevented,” he said.

Concert organizers, Barracuda Music, said in an Instagram post late Wednesday that “we have no choice but to cancel the three scheduled shows for everyone’s safety.” It cited government officials’ confirmation of a planned attack at the stadium.

Swift and her team have not spoken publicly about the plot or canceled shows. Her Instagram page reposted Barracuda Music’s announcement in a “story,” which only last 24 hours.

Last month, an attacker in England killed three girls and wounded 10 other people in knife attack during a Taylor Swift-themed dance and yoga class. Swift at the time said she was ‘’completely in shock’’ over the attack.

Europe is enamored with the American superstar, with the German town of Gelsenkirchen renaming itself “Swiftkirchen” before its mid-July concerts.

Austria’s Vice-Chancellor Werner Kogler wrote on social platform X: “For many, a dream has been shattered today. On three evenings in Vienna, tens of thousands of #Swifties should have celebrated life together.”

“I am very sorry that you were denied this. Swifties stick together, hate and terror can’t destroy that,” Kogler added.

Austrian Chancellor Karl Nehammer posted on X that “the cancellation of the Taylor Swift concerts by the organizers is a bitter disappointment for all fans in Austria.”

“The situation surrounding the apparently planned terror attack in Vienna was very serious,” he wrote. But he added that, thanks to intensive cooperation between police and Austrian and foreign intelligence, “the threat could be recognized early on, tackled and a tragedy prevented.”

Barracuda Music said that “all tickets will be automatically refunded within the next 10 business days.” The same wording was posted under the Vienna dates on Swift’s official website.

The Vienna stadium had been sold out for the planned concerts, APA reported, with an estimated 170,000 fans expected for the concerts in Austria. Some who posted on X lamented months of now-wasted efforts to make friendship bracelets and pick out fashionable outfits for the performance.

Swift is expected to perform at London’s Wembley stadium in five concerts between Aug. 15 and 20 to close the European leg of her record-setting Eras Tour.

In 2017, an attack at an Ariana Grande concert in Manchester, England, killed 22 people. Suicide bomber Salman Abedi set up a knapsack bomb in Manchester Arena at the end of Grande’s concert as thousands of young fans were leaving. More than 100 people were injured. Abedi died in the explosion.

An official inquiry reported in 2023 that Britain’s domestic intelligence agency, MI5, didn’t act swiftly enough on key information and missed a significant opportunity to prevent the bombing, the deadliest extremist attack in the United Kingdom in recent years.

Dazio and Grieshaber reported from Berlin. Associated Press writers Geir Moulson in Berlin, and Jan M. Olsen in Copenhagen, Denmark, contributed to this report.