Are there places where Pokémon should not be allowed to tread?

The digital creatures, which appear overlaid on the real world as part of the hit smartphone game “Pokémon Go,” have been reported at the former concentration camp Auschwitz in Poland, the U.S. Holocaust Memorial Museum in Washington and the National September 11 Memorial in New York, provoking frustrated responses from the representatives of some of the sites.

A spokesman for the Auschwitz Memorial said that any presence of the game there, or at any other memorials and Holocaust museums, was “absolutely inappropriate.”

“Allowing such games to be active on the site of Auschwitz Memorial is disrespectful to the memory of the victims of the German Nazi concentration and extermination camp on many levels,” the spokesman, Pawel Sawicki, said in an email.

He added that the makers of the game had already been contacted, and asked “not to allow the site of Auschwitz Memorial and other similar sites to be included in the game.”

A spokeswoman for Niantic Inc., the gaming startup that teamed with the Pokémon company to make “Pokémon Go,” pointed out that the game is not yet officially available for download in Europe.

However, some sites have posted instructions for obtaining the game in countries outside of the United States, Australia or New Zealand, where it is available. Also, someone who has downloaded it in those three countries would be able to find the creatures in Europe. Niantic’s first game, another augmented-reality app called “Ingress,” exists in Europe, and “Pokémon Go” uses information from that app to inform its digitally enhanced world.

Brian Feldman, a journalist for New York magazine, which reported the Pokémon at Auschwitz, said that the person who sent in the tip was on vacation from the United States and had been able to download the game from the U.S. app store.

Niantic did not have anyone available who could respond to further requests for comment.

A spokesman for the Holocaust Memorial Museum in Washington said that the museum was also working to be excluded from the game.

“Playing ‘Pokémon Go’ in a memorial dedicated to the victims of Nazism is extremely inappropriate,” Andrew Hollinger said in a statement.

“Technology can be an important learning tool, but this game falls far outside of our educational and memorial mission,” he added.

Niantic has struggled to handle the sudden popularity of “Pokémon Go,” which was released in the United States on July 6. Its servers have had a hard time contending with the masses of people attempting to play, and the game’s official introduction in other countries has been delayed because of the unexpected demands.

Pokémon have also appeared in Iraq on the front lines of the fight against the Islamic State, and the Marine Corps joked on Twitter that one had been spotted on a gun range, prompting some protest (and plenty of support).

A military base in Washington state, in a Facebook post, warned “budding Pokémon Trainers” to avoid chasing “into controlled or restricted areas, office buildings, or homes on base.”

Louis Park, the Marine Corps veteran who posted a picture of himself playing from Iraq, used another Facebook post to express his disappointment that it had taken “pop culture” to draw attention to the fight against the Islamic State. He has since made his account, including the original post, private.

“I just made the picture post to be cheeky,” he wrote. “I love Pokémon.”