Alejandro N. Mayorkas, the secretary of the Department of Homeland Security, tested positive on Tuesday morning for the coronavirus, his spokeswoman said.

The secretary, who is vaccinated, learned of his infection during routine testing ahead of a foreign trip.

“Secretary Mayorkas is experiencing only mild congestion,” the department’s spokeswoman, Marsha Espinosa, said in a statement. “He is fully vaccinated and will isolate and work at home per C.D.C. protocols and medical advice.”

Ms. Espinosa said that officials have begun tracing those who had been in recent contact with Mr. Mayorkas.

Mr. Mayorkas was near President Biden at an outdoor event on Saturday for the National Peace Officers Memorial Service, Ms. Espinosa said.