Riverside police are reporting their first encounter with players of the augmented reality game Pokemon Go, a game where people use their cellphones to hunt for virtual Pokemon characters in real-world settings.

While the game was intended as harmless fun, it has had the unintended consequence of putting some players in dangerous situations.

Riverside Police Chief Thomas Weitzel intervened in one such potential situation when he ushered a group of boys away from the Des Plaines River on Wednesday morning, just as two of them were set to cross the stream into Riverside Lawn, where the game was directing them to go.

No one was hurt and the boys in the water had only waded into less than knee-deep water when Weitzel arrived on the scene. Still, he said, the boys were between the ages of 10 and 13 and the situation had the potential to be dangerous.

“Some of my concerns are the waypoints in the game that may not be geographically safe and some areas are more dangerous than others,” Weitzel said in a press release. “I just wanted to make sure the kids who were playing this game were safe and advised them to take their fun to the parks.”

Weitzel said he was pulling into the rear of the police department parking lot at about 8 a.m. on July 13 when he saw a group of eight boys, all looking down at their cellphones, standing at the edge of the river.

As he pulled into the parking space, Weitzel realized that two of the boys were in the river. He reportedly ran to the water’s edge, told the boys to get out of the water and asked what was going on. That’s when the boys told him they were playing Pokemon Go and that were headed toward Riverside Lawn.

None of the boys were from Riverside, said Weitzel. They were from either Lyons of Brookfield and had followed the game to Riverside. Pokemon Go, a free-to-download mobile game, was released in the U.S. on July 6.

Since its release, the game has become a phenomenon with more than 15 million people worldwide downloading the app, according to the technology review publication CNet.

But the game has also drawn criticism for placing its players in inappropriate or dangerous situations. The Washington Post has reported that both the National Holocaust Museum and Arlington National Cemetery have had to issue notice asking people to refrain from playing the game on their grounds.

On Friday, the Illinois National Guard issued a press release announcing that the game was not being allowed on their bases after reports of several people showing up at post gates asking to be let in to play the game.

It’s unclear whether anyone had approached the gate at the North Riverside Armory with such a request. But Lt. Col. Brad Leighton, public affairs officer for the Illinois National Guard, said it wouldn’t surprise him. He said he knew of such incidents at Camp Lincoln in Springfield and at Illinois National Guard Training center in Marseilles.

“We’re just not going to play games when it come to our safety,” Leighton said. “Throughout the state we’ve had people come to our gates asking to get in there.”

Leighton said the National Guard is reaching out to the makers of the game to get their bases removed.

“Nothing against Pokemon or these fun-loving people playing it,” Leighton said. “But it’s a force protection issue for us.”

On Thursday, the Los Angeles Times reported that two men playing the game were injured when they fell off a bluff overlooking over the Pacific Ocean near San Diego. Near Anaheim, meanwhile, a man playing Pokemon Go who wandered into a park in the early morning hours of July 13 was attacked and stabbed by a group of people.

Two other men were reportedly robbed and car-jacked while playing the game in a park in Sacramento County on July 13.

This article has been changed to correct details regarding Pokemon Go players who fell off a bluff overlooking the Pacific Ocean near San Diego.