(NEXSTAR) – Department of Homeland Security Secretary Alejandro Mayorkas tested positive for COVID-19 Tuesday morning, according to his office.

Mayorkas, who is fully vaccinated, found out he had the virus after taking a routine test before traveling, DHS spokesperson Marsha Espinosa said in a tweet.

The secretary is working from home and in isolation. He has only experienced mild congestion, Espinosa added.

It’s not yet clear how he contracted the coronavirus and contact tracing is underway.

A photo taken Saturday shows Mayorkas attending the Annual National Police Officers’ Memorial Service at the U.S. Capitol, standing just a few feet away from President Biden and the first lady. No one in the photo is wearing a mask.

Biden, who is also fully vaccinated, received a Pfizer booster shot in late September.