But though they made dozens of teens take breath tests, none tested positive for alcohol. That's because the keg contained root beer.
The party was held by a high school student who wanted to show that teens don't always drink alcohol at their parties. It has gained fame on YouTube.com.
Dustin Zebro, 18, said he staged the party after friends at D.C. Everest High School got suspended from sports because of pictures showing them drinking from red cups.
The root-beer kegger was "to kind of make fun of the school," he said. "They assumed there was beer in the cups. We just wanted to have some root beer in red cups and just make it look like a party, but there actually wasn't any alcohol."
Zebro purchased a quarter-barrel of 1919 Classic American Draft Root Beer, and by 10 p.m. Saturday, the scene outside his rural Wausau home had all the makings of a teen drinking party - cars, noise and kids.
Kronenwetter Police Chief Daniel Joling said an officer was dispatched to the home March 1 on a complaint of cars blocking the road.
Juveniles began coming out of the house after the officer used his squad car's loudspeaker to warn that cars would soon be towed, Officer Jason Rasmussen wrote in his report.
Nearly 90 breath tests were done, and officers even searched locked rooms for hiding teens.
"It was a tremendous waste of time and manpower, but we still had a job to do, and our officers did it," Joling said. "If one kid had come there, even hadn't drank there, but had come there and had been drinking and had left and crashed and burned, then what would the sentiment be? Why didn't the police check everybody out?"