One person has been killed and dozens injured after a car smashed into pedestrians on a Las Vegas Strip pavement.
Police spokesman Lieutenant Peter Boffelli said the car was travelling north on Las Vegas Boulevard, near Bellagio Way, when it went on to the pavement in front of the Paris Hotel & Casino and struck pedestrians.
Thirty-seven people were taken to hospital.
One person was killed and seven were in a critical condition, authorities said.
"This is a huge tragedy that has happened on our Strip," Mr Boffelli said.
The Miss Universe pageant was being held nearby at the Planet Hollywood Las Vegas Resort & Casino at the time.
Clark County fire chief Greg Cassell said the call for help came in at 6.38pm on Sunday (2.38am today GMT) and 70 emergency crew members rushed to the scene.
Mr Boffelli said the counter-terrorism unit was at the scene but a motive had not been determined. "(It's) unknown if it's an intentional act or impairment act," he said.
Las Vegas police officer Jesse Roybal said the incident did not appear to be a terrorist act.
The woman driver left the scene but was later taken into custody and was being interviewed and tested for alcohol and controlled substances, police said.
Danita Cohen a spokeswoman for University Medical Centre in Las Vegas, said crash victims were brought to its trauma centre.
Sunrise Hospital and Medical Centre was treating 11 adults, who were said to be in good condition
Nevada governor Brian Sandoval said: "The state stands ready to help and will provide any assistance needed to ensure the safety of our visitors and residents."
He said he and his wife Kathleen "extend our deepest sympathies to all who are affected by this shocking and tragic event" and thanked first responders and medical teams caring for the victims.
Joel Ortega, 31, of Redlands, California, and his wife Carla were in Las Vegas for the weekend and came across a police blockade near the crash scene.
"At first, I thought it was a movie shoot," Mr Ortega said. "I thought maybe we'd see someone famous."
Mr Ortega said the couple remembered how their neighbourhood was disrupted after the December 2 mass shooting in San Bernardino, California, near their home.