WASHINGTON – Vice President Mike Pence visited the Mayo Clinic on Tuesday to tour facilities supporting research about the coronavirus, but he appeared to violate the hospital's policy during his tour by not wearing a mask.

Video of his tour shows Pence walking through the Rochester, Minnesota, medical center to meet with staff and patients, but without wearing a mask.

Mayo Clinic policy requires "all patients, visitors and staff to wear a face covering or mask while at Mayo Clinic to guard against transmission of COVID-19."

The Mayo Clinic's Twitter account later responded to Pence's visit, tweeting that they had "informed @VP of the masking policy prior to his arrival today." The tweet has since been deleted.

The Mayo Clinic tweeted later in the afternoon to say it was "grateful" for the visit from Pence and Minnesota Governor Tim Walz and looked "forward to continued collaboration to develop essential testing and treatment for our patients and communities."

Speaking to reporters following his visit, Pence said he did not wear a mask because he did not have the coronavirus and was following CDC guidelines about wearing masks to prevent the spread of the virus by those who are infected with it but might not have symptoms.

"As Vice President of the United States I'm tested for the coronavirus on a regular basis, and everyone who is around me is tested for the coronavirus,” Pence said.

"And since I don't have the coronavirus, I thought it'd be a good opportunity for me to be here, to be able to speak to these researchers, these incredible healthcare personnel, and look them in the eye and say thank you."

Current guidelines from the Centers for Disease Control and Prevention recommend the wearing of a mask in public to help stop the spread of the coronavirus.

President Donald Trump has declined to wear a mask.

"I don't think I'm going to be doing it," he said when the Trump administration rolled out its guidance on masks.

First lady Melania Trump, however, has urged Americans to wear masks and shared posts on her social media accounts of herself wearing a face mask.