THE HAGUE, Netherlands -- Police in the Dutch port city of Rotterdam detained the driver of a van with Spanish license plates and a number of gas tanks inside after a concert by an American rock band was cancelled Wednesday night following a threat, the city's mayor said.

Rotterdam Mayor Ahmed Aboutaleb said at a hastily arranged press conference that the van's Spanish driver had been detained and was being questioned by police on Wednesday night. Military explosives experts were deployed to Rotterdam to examine the van, police said.

Aboutaleb says the concert by Los Angeles band Allah-Las was called off after Dutch police received a terror warning from Spanish police.

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Late Wednesday, Spanish counterterrorism official says the van is not connected to last week's deadly vehicle attacks that killed 15 people.

Authorities search a van that was stopped in Rotterdam on Wednesday night not far from a concert venue where a show by American rock band Allah-Las was canceled due to an unspecified threat. Reuters

The official said investigators discarded a possible link between the van's driver and the extremist cell that carried out the attacks in and near Barcelona after questioning the driver and examining the van.

Concert organizer Rotown said earlier on Twitter that the concert venue, a former grain silo called Maassilo, was being evacuated because of the unspecified threat and concertgoers would get their money back.

Rotterdam police said they took the information about a threat "seriously enough that after discussion with organizers it was decided to cancel the event."

A picture shows a general view as police evacuate the Maassilo concert venue after a concert by Californian ban Allah-Las was canceled in relation to a terror attack threat, according to police and the venue, on Aug. 23, 2017. Getty

Dutch television showed officers in body armor outside Maassilo and what appeared to be members of the band leaving the venue in a white van with a police escort.

In an email to The Associated Press, the band's label, Mexican Summer, said: "Due to a potential terror threat at The Maassilo in Rotterdam, the Allah-Las show was canceled tonight.

"Details are not available at this time as the incident is still under investigation. The band is unharmed and are very grateful to the Rotterdam Police and other responsible agencies for detecting the potential threat before anyone was hurt."