He said that the photograph that has been circulating on social media was the only one he was aware of showing the sign in such an inappropriate place, and added that he was not aware of any other similar incidents.

Mr. Crowson would not comment further about the possibility that the widely shared photo had been doctored.

After people began sharing the photo on social media on Wednesday morning, members of the company’s social media team initially said on Twitter that the sign had been hung inside a store in Evansville, Ind., and that it had been subsequently removed from the gun display.

But, in fact, Mr. Crowson said, there had been “miscommunication” between a store employee and a member of Walmart’s social media team who had called the store.

“It was never confirmed the sign was there, and it wasn’t confirmed that this was the store in question,” Mr. Crowson said. He added that members of the social media team had sent tweets correcting the early misinformation.

Mr. Crowson said the company had “quite a few people” investigating the origins of the photo as of Thursday night, but he could not say exactly when officials expected to get to the bottom of what happened.