Police Go on Party Patrol

A new system used by authorities monitors underage parties posted on social media sites.
3:00 | 01/10/14

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Transcript for Police Go on Party Patrol
The new way police are cracking down on out-of-control house parties much the guest list, it can quickly escalate to dang dangerous levels. Abc's gio benitez went along with police who are using teen tactics to stop the parties. Reporter: Coast to coast they are the parties that have been spiraling out of control. Fueled by facebook and infused by instagram turbocharged by twitter. When jill abbott was on vacation, her son's classmates barged into her house near boston and announced a party on facebook. 100 teens showed up causing $45,000 in damage. The doors had been smashed. My bedroom window was smashed. Just horror. Reporter: Now cops are on the digital trail much the l.A. County sheriff's department creating the nation's first and only specialized unit to watch parties in realtime on social media. Listening for dangerous party buzz. We're on facebook, instagram, twitter. Reporter: Using search terms like party tonight, bring your own beer. Reporter: The unit rolls out and we're there, first stop a teen birthday party seen on facebook. This one boasting of goodies, usually the latest drug of noise, nitrous oxide, nod, the gas yoin a dentist's office. We saw a couple tanks, fill the balloons with the gas and kids inhale the gas out of the balloons. Reporter: Illegal noz tanks are everywhere. We would be making arrests if those tanks were full. Okay. Reporter: Parents are surprised the parties were online. I didn't believe it. He showed me the flier. Reporter: That's what you said. What, it's on the internet? Yes. Showed me the flier and it showed that that tank was going to be here and the beer. Reporter: Leading cops right to where the party is at. For "good morning america," gio benitez, abc news, new york. All right, gio, thank you. You can see more of his report on a special "20/20" at 10:00 eastern right here on abc.

This transcript has been automatically generated and may not be 100% accurate.

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