THE HAGUE (AFP) - Dutch police continued to question a man Friday (Aug 25) over a suspected plot against a Rotterdam concert, but doubts grew over the authenticity of the threat which triggered a major security alert.
"We... will continue to question the suspect and our investigation is ongoing," Rotterdam police spokesman Wessel Stolle told AFP, saying there was "not much more" to add.
The 22-year-old suspect, identified by Dutch media as Jimmy F., was arrested during a pre-dawn raid on Thursday in a small village 42 kilometres (26 miles) south of the bustling port city where US rock band the Allah-Las was due to play on Wednesday.
The arrest followed a tip-off by Spanish police on Wednesday afternoon who said they had spotted a message on the Telegram chat-app about a possible terror attack, two Dutch newspapers reported, citing unnamed sources.
Telegram is a smartphone app which has often been used by Islamic extremists due to its encrypted messaging service.
Dutch media said the message appeared to have been posted online by the suspect, with some newspapers suggesting it may have been a prank which backfired.
"The decision to cancel the Allah-Las concert was mainly based on one chat message," the authoritative NRC daily reported.
"The terror threat in Rotterdam came from the 22-year-old," said the centre-left De Volkskrant. Neither report was confirmed by the police.
Dutch Justice Minister Stef Blok had on Thursday denounced the suspect's actions as "idiotic" fuelling doubts over the authenticity of the threat.
But on the same day, Rotterdam police chief Frank Paauw told AFP that the threat was concrete and specific.
"There was concrete information from the Spanish police that an attack would be committed on that date, at this place and against this rock band." .
Neighbours of the suspect living in the southern town of Zevenbergen described him as a "quiet youngster who still lived with his parents." "He is a seemingly ordinary student that has a second job at a petrol station and who every-now-and-then drinks a beer at the local pub," daily tabloid De Telegraaf said.
Dutch media said he had taken part in chat groups discussing the war in Syria but that he had demonstrated "no radical viewpoints." But police said it was too early to say if it was a prank.
"At this stage it is too early to say whether it was indeed a joke," Stolle told AFP.
Anti terror experts said the Spanish tip-off was not thought to be linked to last week's deadly vehicle attacks in Barcelona and the Spanish seaside town of Cambrils in which 15 people were killed and another 120 wounded.
"But, seen in the recent context of the attacks in Spain... it is understandable that alarms bells went off," Leiden University expert Jelle van Buuren told the Trouw newspaper.
There were also growing doubts among the Dutch public Friday whether the threat was indeed real, with a public discussion on the issue sending off a stream of comments on Twitter.
"Seriously wondering whether there was an actual #threat. I suspect possible #overkill by the #police," wrote one person identified as "Echo".
Late on Thursday, police released another man who was arrested near the venue, saying the driver - who was in a white van with Spanish plates containing gas bottles - was most likely "in the wrong place at the wrong time." He was arrested after police noticed him driving suspiciously near the Maassilo concert venue in the city's sprawling harbour district.
Police later said he was drunk and released him saying he was no longer a suspect in the case.
The Netherlands has so far been spared the terror strikes that have rocked its European neighbours recently.
But top Dutch security and intelligence officials have been keeping a wary eye on events.
In June, a Dutch man - known to authorities as being possibly radicalised - was arrested filming outside a stadium during a concert. He was later freed, but the incident is still under investigation.