A police officer with a holstered gun who was escorting a group of teenagers prompted a brief lockdown Tuesday at Princeton University, the school posted on its website.

A shelter-in-place order was issued for the college campus just before noon after a security guard spotted a person with a handgun in the Princeton University Art Museum. 

Officials said the person with the gun was identified as a police officer who escorting a group of teens on an exchange program for a tour of the museum’s galleries. The officer, who was wearing a badge but was not in uniform, was carrying the gun in a holster.

The gun was never removed from the holster, university officials said.

The officer, who did not alert museum staff to his presence in advance, is cooperating with officers who responded to the incident, according to the post of Princeton’s website.

The shelter-in-place order was in effect for about 10 minutes.

No additional details were immediately available.