Police blew up a plastic grocery bag filled with fuses and electrical wire Thursday, calling the package near the Olympic media center a "hoax device."

Police said the bag might have been designed to see how authorities would react. It contained no explosives.

"There's some concern it was like a trial run," said Craig Gleason, a police department spokesman.

The bag was left near a parking garage several blocks from the media center, in a downtown area increasingly crowded with Olympic pedestrians the day before the opening ceremony. Security officials were studying videotapes for clues.

"The package was, in fact, a hoax device," the Olympic Joint Terrorism Task Force said in a statement. "This was not an exercise."

The bag was found around noon by construction workers, who notified security guards. A police bomb squad detonated a device next to it to make sure it wasn't an explosive, then set off a second small explosion to make sure the bag was destroyed.

"It was absolutely not an explosive device," Gleason said. "It appears to be a white bag full of fuses and red and white electrical wire."

Officials vowed to prosecute anyone involved in the hoax.

Police evacuated two nearby buildings and military helicopters began hovering over the area. The FBI and agents from the Bureau of Alcohol Tobacco and Firearms were also on the scene.

The quick response by various police agencies is proof the Olympic security plan is working, said Robert Flowers, head of the Utah Olympic Public Safety Command.

"Everything is going the way it's supposed to," he said.

The site is about 40 yards from the Federal Reserve Building and across the street from the Gallivan Center, a park were organizers will hold some Olympic-related festivities.

Salt Lake City Mayor Rocky Anderson said he was satisfied with the police response.

"I'm not concerned. We're going to run into these things all the time," Anderson said.