In a high-tech hunt for hooligans, Dutch police sent 17,000 text messages to the mobile phones of fans who attended a soccer match marred by rioting.
Supporters rioted before, during and after the April 17 match in Rotterdam. Two train cars were vandalized beyond repair, 43 fans were arrested and 47 police officers and an unknown number of fans were injured.
Phone companies voluntarily handed over the mobile numbers of people who were in or around the stadium that day. The companies did not give individual names to police, and police sent a standard message asking people to come forward if they had information.
But some suspects apparently thought they had been fingered. Four suspects contacted police Wednesday, and a fifth turned himself in directly, Rotterdam police spokesman Ger de Jong said.
"Maybe they just think, 'I'm going to get caught sooner or later so I better just turn myself in and get it over with,'" de Jong said.
Rotterdam police also filmed the clashes and have posted images of suspects on their Web site, drawing complaints from privacy groups.
De Jong said the posting the images contributed to 100 additional arrests in the months after the game.
The text messages and Internet site were extensions of traditional investigation techniques to new media, de Jong said.
"This is no different than the requests for information we publish in newspapers or on television," de Jong said.