Celtics star Isaiah Thomas’ sister, Chyna, 22, was killed in a one-car accident on Interstate 5 in Washington state early Saturday, multiple outlets reported.

Thomas is expected to play Sunday in Game 1 of the first-round series against the Bulls in Boston, according to multiple reports. Thomas’ father, James, told the Boston Herald that his son hadn’t decided when he would return home to Tacoma to be with family.

According to the News Tribune (Tacoma, Washington), which cited Washington State Patrol and family friends, Thomas’ car, a 1998 Toyota Camry, traveled off the road around 5 a.m. and hit a barrier, which a state patrol spokesman said ‘‘vaulted the vehicle head-on’’ into a signpost.

According to the state patrol, Thomas wasn’t wearing her seatbelt at the time of the accident and died at the scene.

“We are terribly saddened by the tragic loss of Chyna Thomas,” the Celtics said in a statement. “The thoughts and prayers of the entire Celtics organization are with Isaiah and his family.”

NBA commissioner Adam Silver also released a statement: “The NBA family mourns the tragic passing of Chyna Thomas and we send our deepest condolences to Isaiah, his family and the Celtics organization during this difficult time,” Silver said.