A noose was found in the garage stall of black driver Bubba Wallace at the NASCAR race in Alabama on Sunday, less than two weeks after he successfully pushed the auto racing series to ban the Confederate flag at its tracks and facilities.
NASCAR said it had launched an immediate investigation and will do everything possible to find who was responsible and eliminate them from the sport.
"We are angry and outraged, and cannot state strongly enough how seriously we take this heinous act," the series said in a statement.
"As we have stated unequivocally, there is no place for racism in NASCAR, and this act only strengthens our resolve to make the sport open and welcoming to all."
On Twitter, Wallace posted "the despicable act of racism and hatred leaves me incredibly saddened and serves as a painful reminder of how much further we have to go as a society and how persistent we must be in the fight against racism.
"This will not break me, I will not give in nor will I back down. I will continue to proudly stand for what I believe in."
The noose was discovered on the same day NASCAR's fledgling flag ban faced its biggest challenge. The ban took effect before last week's race near Miami, but there were only about 1,000 military members admitted into that race. At Talladega, in the heart of the South, as many as 5,000 fans were allowed in, even though rain postponed the race until Monday.
Wallace, a 26-year-old Alabama native, had found support among fellow drivers for his stance on the flag and he noted that in his tweet late Sunday after the noose announcement.
"Together, our sport has made a commitment to driving real change and championing a community that is accepting and welcoming of everyone. Nothing is more important and we will not be deterred by the reprehensible actions of those who seek to spread hate," he said.