Police made 33 arrests in and around the Kuip stadium in Rotterdam which hosted the KNVB Cup final on Sunday between PEC Zwolle and Ajax.

Underdogs Zwolle thrashed Ajax 5-1 to deny the Amsterdammers the chance of a double. Ajax could clinch the league title next weekend.

Most of the fans arrested had been letting off fireworkers or were drunk and using insulting behaviour. Eight Feyenoord supporters were also picked up who were heading for the stadium, Nos television says.

Six people were also taken to hospital to be treated for firework burns. The match was halted for around 30 minutes after Ajax fans began pelting the pitch with fireworks.

Ajax coach Frank de Boer said after the game the behaviour of the firework throwers was disgraceful and had damaged the club’s reputation. ‘This was nothing to do with football,’ he said.

Searched

Ajax general director Edwin van der Sar said fans had been searched twice and he did not understand where the fireworks had come from. They were searched getting onto the buses and then again to get into the stadium, he is quoted as saying by news agency ANP.

According to the Telegraaf, Ajax faces a fine of at least €15,000 and a supporter ban for at least one match because of the distruption. This is the punishment handed out to FC Utrecht in 2012 after a similar incident.

However, the punishment could be increased because the match involved was the cup final, the paper says.