BERLIN (Reuters) -Austrian police investigating an alleged plot to kill large numbers of people outside the venue of three planned Taylor Swift concerts in Vienna this week have detained four teenagers.
Here is what security officials have said about them.
THE 19-YEAR-OLD
An Austrian national with North Macedonian roots was arrested in the early hours of Wednesday during a police operation at his home in Ternitz, a town near the Hungarian border.
The teen, who had posted a video online confessing to the plot, quit his job on July 25, telling people that he "had big plans", public security chief Franz Ruf told reporters on Thursday.
The suspect had recently changed his appearance and had been consuming and sharing Islamist propaganda online, security officials said, adding that he had pledged allegiance to Islamic State but also held sympathies for Al Qaeda.
A neighbour told Austrian broadcaster Puls24 that the young man kept himself to himself and that he had grown a "Taliban beard".
During a search of his home, law enforcement authorities secured various substances and tools used for building bombs, as well as Islamic State propaganda, 21,000 euros ($23,000) in counterfeit money, machetes, knives and blank ammunition.
The Kurier newspaper, citing sources familiar with the situation, reported that the suspect had stolen the chemicals from his former workplace, a metal processing company also in Ternitz. Officials did not comment on where he got the chemicals from, adding that this was a focus of their investigation.
THE 17-YEAR-OLD
After initially being tipped off to a single suspect, Austrian investigators came across the others, including a 17-year-old Austrian national with Turkish-Croatian roots who was arrested in Vienna on Wednesday afternoon.
He had been acting conspicuously in the area of the Ernst Happel Stadium, where Swift's stadium shows had been due to take place on Thursday, Friday and Saturday. They have now been cancelled.
The 17-year-old had been given a job a few days ago with a company providing services at the stadium.
The boy, who also appears to have been radicalised and was already known to authorities, had recently broken up with his girlfriend, Ruf said.
He is still to make a statement to police so his exact role in the plot is unclear, but he had extensive contact with the main suspect, officials said.
THE 18-YEAR-OLD
As part of investigations into those close to the main suspect, authorities detained an 18-year-old Iraqi national who had sworn allegiance to IS on Aug. 6, the interior ministry said on Friday.
It is unclear whether the Iraqi teenager is directly linked to the actual plans to attack the concert, the ministry added.
According to the Kronen Zeitung newspaper, the suspect is living in Austria as a refugee. Authorities are working to revoke his status and deport him as soon as possible, it added.
THE 15-YEAR-OLD
The fourth teenager to have been detained is an Austrian national with Turkish heritage, officials said.
The 15-year-old, whose role has not been fully clarified, is being questioned intensively by police, said the interior ministry.
According to the Kurier newspaper, the boy was allowed to go home after being questioned as a witness and is not considered a suspect.
During questioning, the youngster said the main suspect had changed considerably in recent months and had also regularly enquired about devices to ignite explosives, officials said.