The game was in mid-flow when the speaker told fans to keep calm and stay in the FC Twente stadium.
A stash of fake weapons has also been discovered in one house in Enschede, during an early-morning police raid of three properties.
One spokeswoman told the NOS that there was evidence that the stadium was used for drug trading during matches, and also that some people were being barred from entry.
She said: ‘From our investigations, it appeared that drug dealing was happening during matches, so we could only ascertain this during a home match.’
Onno van Veldhuizen, mayor of Enschede, said in a press conference on Friday morning that the supporters’ club Vak-P was suspected of organised criminality, apparently involving motorcycle club Satudarah.