Investigations have been launched after a helicopter reportedly crashed after swerving to avoid a consumer drone.
A trainee had been practising hovering about 15m (50ft) above trees on Daniel Island, South Carolina, reported the Charleston Post and Courier newspaper quoting a police report.
Seeing a quadcopter flying towards them, the instructor had taken control.
But he had clipped a tree with the tail rotor, causing the helicopter to crash to the ground and tip on to its side.
The National Transportation Safety Board said it "had not yet been able to independently verify" the pilot's report.
The drone is believed to have been a DJI Phantom.
"DJI is trying to learn more about this incident and stands ready to assist investigators," the company said.
It provided owners with help to ensure they "steer clear" of traditional aircraft, DJI added.
Industry groups representing large US airlines, pilots and air-traffic controllers have previously urged the US Federal Aviation Administration (FAA), which has also launched an investigation into the crash, to end exemptions that currently prevent it from regulating consumer drones.
"The likelihood that a drone will collide with an airline aircraft is increasing," said a letter co-signed by the three organisations.