PHOENIX—The "Pokemon Go" craze across the U.S. has people wandering into yards, driveways, cemeteries and even an off-limits police parking lot in search of cartoon monsters, prompting warnings that trespassers could get arrested or worse, if they cross paths with an armed property owner.
Since the release of the smartphone game last week, police have gotten a flurry of calls from residents about possible burglars or other strangers prowling the neighborhood.
So far, few tickets have been issued, and there have been no reports of arrests or assaults on trespassers playing the game, whose object is use the phone's GPS technology to find and capture animated creatures in real-world places.
"Be careful where you chase these Pokemon—or whatever it is you chase— because we have seen issues in other places with people going onto private property where a property owner didn't want them on there," said Assistant Police Chief Jim McLean in Pflugerville, Texas.
Some players have expressed worries on social media that the game could result in a fearful property owner pulling a gun — a scenario that could fall into a legal gray zone in the nearly two dozen states with "stand your ground" laws that allow people wide latitude to use deadly force when they believe they are in danger.
McLean's department posted a Facebook warning Monday after officers spotted a man playing the game in a section of a police parking lot where the public isn't allowed. The player had to pass keep-out signs and go over a fence or under a gate to reach the area.
"I'm not sure how he got back there, but it was clear what he was doing," McLean said. "He was playing a Pokemon game with his phone up in the air."
In Utah, Ethan Goodwin, 17, of Tremonton, was given a trespassing ticket that he worries could cost him up to $200 after he and a couple of friends went on an early morning Pokemon chase at an abandoned warehouse. He managed to catch three creatures.
"I wouldn't say it was worth it, but I would say I'm glad I have the Pokemon I have now," he joked. He added: "It's a dumb game, really, really stupid."
Every time the app is opened, a warning from game maker Niantic pops up, telling players to be aware of their surroundings. Players must also agree to fine print saying they cannot enter private property without permission.
There's also a disclaimer that says Niantic is not liable for any property damage, injuries or deaths that result while playing.
But those warnings don't seem to be getting through.
In Phoenix, police have started posting humorous and colorful warnings on social media, saying chasing the orange dragon Charizard is not a valid reason to set foot on someone else's property.
And neither is chasing the cat-like Mewtwo, according to Boise, Idaho, police. They posted a Facebook message saying officers responded to several calls about players trespassing on private property and illegally trekking across parks after dark.
Gamers are also being warned to watch for traffic while playing and not to drive while on the app.
One woman told WPXI-TV in western Pennsylvania that her 15-year-old daughter was hit by a car while playing the game and crossing a busy highway. The girl was hospitalized with an injured collarbone and foot, as well as cuts and bruises, said her mother, Tracy Nolan.
Capt. Michael Fowler with the Hanahan, South Carolina, police said his department in the city of about 20,000 has gotten a few suspicious-activity reports related to "Pokemon Go," including multiple calls from a woman who feared for her safety as she watched cars go in and out of a church parking lot across from her house.
"I didn't know what was going on. The last time I heard about Pokemon was back in the '90s," Lynn Menges, 59, said.
Lt. Lex Bell, of the Unified Police Department in Utah, said officers outside Salt Lake City have responded to similar calls. Most come after dark, with residents saying they believe motorists driving slowly through their neighborhood may be casing their homes. In one instance, a woman mistook a few glowing cellphones for flashlights as players hunted characters near her daughter's car.
Several cemeteries, including Arlington National outside Washington, have expressed worries about players on their grounds.
At Mobile Memorial Gardens in Alabama, president Timothy Claiborne said he has seen visitors walking or driving around with phones in their hands, playing the game. He asked people in about three dozen vehicles to leave over the past couple of days, earning him the title "chief of the Pokemon patrol" from the staff.
"I just think we need to continue to have respect not only for the dead but for those who are grieving the dead," he said.