USA Basketball announced that a player had entered the protocols but didn't name the player.
Beal, who played 30 minutes in Team USA's win over Argentina on Tuesday night, is expected to have more clarity on his status by Thursday, sources said.
There is a possibility that Beal's situation could leave him unable to play at the Tokyo Games, but that hasn't yet been confirmed. He played his best exhibition game of the pre-Olympic schedule Tuesday, scoring 17 points with six rebounds and three assists.
If Beal cannot play, Team USA has the option to replace him on the roster. Three members of the Select Team are playing in the exhibition games: Keldon Johnson of the San Antonio Spurs, Darius Garland of the Cleveland Cavaliers and Saddiq Bey of the Detroit Pistons.
Last week, three members of the USA Select roster left the team because of health and safety protocols. One player tested positive for COVID-19 and two left because of contract tracing measures, sources said.
Team USA was off Wednesday and is next scheduled to play Friday against Australia.
The Athletic first reported that Beal had entered health and safety protocols.