On Monday night, the Secret Service urged Pence’s staff to delay the Tuesday trip until Wednesday because at least one agent on the ground had a confirmed case of covid-19 and other agents and federal officers preparing for the Arizona visit were showing signs of illness, according to two administration officials.

The Secret Service needed time to bring in healthy agents and other personnel to replace the ones who were either sick or most likely sick, one of the officials said. The official said the Secret Service estimated that a total of eight to 10 agents and other officers from sister agencies — all of whom were helping prepare for Pence’s visit to Arizona — had fallen ill.

This is the second time in recent weeks that Secret Service agents preparing for a White House or Trump campaign event outside Washington have contracted the virus. At least three Secret Service personnel working on the advance team for President Trump’s Tulsa rally on June 20 tested positive for the coronavirus. Two agents tested positive hours before the indoor stadium event was held, and dozens of agents who were on site for the rally were ordered to self-quarantine when they arrived home.