"She has been busy and focusing on work," a source close to Stefani tells PEOPLE. The singer has been back on the Los Angeles set of the hit reality competition alongside her fellow co-stars Blake Shelton, Adam Levine and Pharrell Williams.
Stefani, 45, and Rossdale, 49, who were married for nearly 13 years and together for 20, shocked fans when they announced their split earlier this month.
"While the two of us have come to the mutual decision that we will no longer be partners in marriage, we remain partners in parenthood and are committed to jointly raising our three sons in a happy and healthy environment," the duo told PEOPLE in a statement. "To that end, we respectfully request privacy from the media during this time."
Though the No Doubt singer has expressed her excitement on returning to The Voice's ninth season, her main focus will continue to remain on her children – Kingston, 9; Zuma, who turns 7 this month; and Apollo, 17 months – during this sensitive time.
"Knowing how she is as a mom, her top priority is making sure her kids feel secure and comforted during the process," a source close to Stefani previously told PEOPLE.