The Dutch government is investigating if possible warning signs from Israel were missed in the events leading up to this week’s assaults on Israeli soccer fans, justice minister David van Weel said in a letter to parliament.

“An investigation is still being conducted on possible warning signs from Israel”, Van Weel said in his letter late on Friday evening.

At least five people were injured during the assaults on Thursday night and treated in hospital. All were released later on Friday. The incident concerned fans of the visiting Maccabi Tel Aviv soccer team.

The police on Saturday said four people remained in custody of the 63 people initially detained.

“The Public Prosecution Service has stated that it aims to apply fast-track justice as much as possible”, Van Weel said, adding that it is “the absolute priority” to identify every suspect.

He said the investigation would also examine whether the assaults were organised, with an antisemitic motive.

Political leaders have already denounced the attacks as antisemitic. Dutch Prime Minister Dick Schoof said on Friday he was “horrified by the anti-Semitic attacks on Israeli citizens” and had assured Israeli Prime Minister Benjamin Netanyahu by phone that “the perpetrators will be identified and prosecuted”.

Israel sent extra planes to The Netherlands to bring fans home, but a Dutch government spokesperson could not immediately confirm how many people made use of this.

Videos on social media on what happened showed riot police in action, with some attackers shouting anti-Israeli slurs. Footage also showed Maccabi Tel Aviv supporters chanting anti-Arab slogans before Thursday evening’s match. Amsterdam banned demonstrations through the weekend and gave police emergency stop-and-search powers in response to the unrest.

Antisemitic incidents have surged in the Netherlands since Israel launched its assault on the Palestinian enclave of Gaza after the attacks on Israel by Hamas militants in October last year.

Protests banned

Amsterdam banned demonstrations for three days from Friday.

Mayor Femke Halsema said Maccabi Tel Aviv fans had been “attacked, abused and pelted with fireworks” around the city, and that riot police intervened to protect them and escort them to hotels.