Associated Press reporter Jenna Fryer has reported that 14 people were treated on site, while 14 were transported offsite after the NASCAR crash in Daytona, Florida.
14 people treated on site, 14 people transported off site.
More top news
Many police are said to have been seriously wounded in the attack which may have been targeted at them, officials said.
Syrian government forces are continuing a push for total control of Aleppo, while a reported 20,000 civilians left the city on Saturday.
Rex Tillerson is president of Exxon Mobil and has close business links to Russian President Vladimir Putin.