At least four people who were at the Republican National Convention tested positive for the new coronavirus, Mecklenburg County, North Carolina’s health department confirmed.

The four-day Republican National Convention concluded on Thursday with President Donald Trump formally accepting a renomination to be his party’s candidate for president. His official re-nomination was solidified on Monday when he received the 1,276 delegates necessary to become the nominee, 336 of which ventured to Charlotte, North Carolina, to appear in person.

Of the four people to test positive, two were attendees and two were event support people, Mecklenburg County posted on Twitter. They were all immediately isolated.

Upon arrival, the RNC required delegates to wear masks and partake in temperature checks, as well as, wear a fob that tracks who they come into contact with, according to NPR. RNC’s health consultant, Dr. Jeffrey Runge, said the data collected from the trackers will be used if someone gets infected with COVID-19.