Vienna, Austria - The main suspect in a plot to attack a Taylor Swift concert in Vienna allegedly planned to drive his car into a crowd of fans on either Thursday or Friday, with the goal of killing as many people as possible, investigators said.

The 19-year-old man had planned to use an explosive device and cutting and stabbing weapons in the attack outside the Ernst Happel Stadium, where Swift was scheduled to perform, Austrian investigators said on Friday.

The suspect has confessed, according to police.

Swift's three Viennese concerts were cancelled for security reasons, leaving tens of thousands of fans very disappointed.

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On Friday, Austrian Interior Minister Gerhard Karner said an 18-year-old man from Iraq, who had pledged allegiance to the terrorist group Islamic State, had been arrested.

The minister said that the 18-year-old was travelling with the 19-year-old main suspect, though he was not directly involved in the attack plans. The two young men reportedly knew each other casually, officials stated.

The 19-year-old was arrested on Wednesday, as was a 17-year-old suspect who was working as a stage and scaffolding builder in the concert venue and is a friend of the principal suspect. While the oldest teen confessed, the youngest one has refused to talk, officials said.

A Vienna regional court on Friday issued a pre-trial detention order for the two, a court spokeswoman said. The order, which is initially limited to August 23, was issued due to the risk of committing a crime, the court said.

The suspects are being investigated for membership in a terrorist association and criminal organization. They are accused of having links with Islamic Staten and of having espoused its goals and intentions, a spokeswoman for the public prosecutor's office told the Austrian news agency APA.

The main suspect hinted to two friends that he intended to carry out a terrorist attack, the Austrian news agency APA reported on Friday.

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When he quit his job at a chemical company, he mentioned having "big plans." He is said to have stolen the necessary chemicals to build a bomb from his former employer.

As of Friday afternoon, the 19-year-old did not have a lawyer.

Investigators said that the young man, who was registered with his parents in the town of Ternitz to the south of Vienna, exhibited signs of psychological instability.

He had recently undergone a noticeable change in appearance, reportedly to match the typical image of an Islamic State fighter. He stopped shaving. Additionally, he is believed to have taken anabolic steroids to gain muscle mass.

The main suspect's family comes from North Macedonia and the second suspect, the 17-year-old's family has Turkish-Croatian roots. The younger teen was already known to state security officials.

A 15-year-old, considered a witness, continues to be interrogated intensively, said Karner.

The investigations are continuing at full speed, and the public will be informed as soon as there are new findings, the interior minister said.

The US said on Friday it shared intelligence information with the Austrian authorities in the case.

Meanwhile, the many thousands of Swifties tried to make the best of not being able to see their idol by gathering in the city to sing the star's songs, exchange the friendship bracelets, and take countless selfies.

Some venues offered free drinks to fans as a consolation for the missed event.