Dutch police arrested a man on Thursday and questioned him on suspicion of preparing an attack on a concert in Rotterdam by an American rock band.
But the Dutch justice minister suggested later in the day that the suspect may only have sent a threatening message.
The 22-year-old man was being interrogated to determine exactly what his role was in the threat, police spokeswoman Svetlana Westermeijer said.
No charges had been filed yet.
The arrest in a town identified by Dutch media as Zevenbergen, south of Rotterdam, came hours after police cancelled a performance Wednesday night by the Los Angeles band Allah-Las at a converted grain silo in the heart of the port city following a tip-off from Spanish authorities.
"The suspicion is that the suspect is involved in the preparation of a terrorist attack," Rotterdam Police Chief Frank Paauw said.
"There is no terror threat now anymore," he added.
"There is no threat because we have arrested a suspect and the information about the threat was so specific on the location of the event that, with that arrest, we can conclude that the threat is gone."
If authorities want to prolong the suspect's detention, they will have to arraign him at a closed-door hearing with an investigative judge before the end of Friday, prosecution spokeswoman Jeichien de Graaff said.
Police searched the man's home after his arrest but released no details of anything they found.
His identity was not released, in line with Dutch privacy guidelines.
Security and Justice Minister Stef Blok, in an interview with BNR radio, suggested the suspect may only have spread the threat on a social media platform.
"The person who spread the message has been picked up and he will be questioned," Mr Blok said in a reference to the man's arrest.
"We are very curious to hear from him why he carried out this idiotic action."
Meanwhile, a Spanish mechanic detained on Wednesday night while driving a white van containing a number of gas canisters close to the concert venue was released without charge.
"Investigations showed there was no link between the man and the terror threat," police said in a statement Thursday night.
Dutch counter-terror coordinator Dick Schoof commended the police action and left the country's threat level unchanged at "substantial," the fourth step of a five-level scale.
It was not clear what the nature of the threat to the concert was.
In an interview with The Guardian last year, band members said they chose the word Allah, Arabic for God, because they were seeking a "holy-sounding" name and did not realise it might cause offence.
Police in Warsaw, Poland, beefed up security for the band's performance there on Thursday night, checking a few hundred fans as they arrived at the Niebo (Heaven) club.
Joanna Konieczna, 32, was excited that she would be hearing her favourite band live.
"The events in Rotterdam did not scare me, I feel very safe in Poland," she said.
Spain, already on high alert following last week's deadly attacks in and near Barcelona that killed 15 people and injured more than 120 others, played a key role in the events of Wednesday and Thursday.
A Spanish counter-terrorism official said Spain's Civil Guard received "an alert indicating the possibility of an attack in a concert that was going to take place in Rotterdam".