Williamson, the Pelicans' second-leading scorer at 23.6 points per game, departed the Walt Disney World Resort complex in Florida last week to attend to what the team termed "an urgent family matter".
"[Williamson] has been getting tested daily for COVID-19 while away from the team and continues to produce negative results," the Pelicans said in a statement.
"While there is no current timetable for his return to campus, he fully intends to rejoin the team."
Per NBA protocols, Williamson will be required to quarantine for between two to four days once he returns to Orlando, as long as he continues to be tested daily for COVID-19. Failure to undergo daily testing would require a quarantine period of at least seven days.
Provided the 20-year-old rejoins the Pelicans within the next week and remains negative for the virus, the 2019 first overall draft pick could be cleared to play in New Orleans' first scheduled game of the NBA's restart against the Utah Jazz on July 30.
Williamson missed New Orleans' first 44 games while recovering from arthroscopic surgery on his right knee but made a significant impact upon returning from the injury. The Pelicans were 17-27 and in 12th place in the Western Conference when the former Duke standout made his delayed debut on January 22, and the team has gone 10-9 with him in the lineup.
New Orleans enter the restart in 10th place in the West, 3.5 games behind the eighth-placed Memphis Grizzlies.