Authorities in the US state of Kentucky have warned the death toll from a UPS cargo plane crash is likely to rise above nine.

Investigators from the National Transportation Safety Board have now arrived at the scene to try and work out the cause of the crash, which has shocked the community.

Emergency service crews searched for more victims on Wednesday (Thursday AEST) after the plane crashed and exploded in a massive fireball at the company's global aviation hub in Kentucky, creating an inferno that consumed the enormous aircraft, authorities said.

Governor Andy Beshear predicted the death toll would grow, noting that 16 families had gathered at a reunification centre for news of loved ones.

The crash was captured in horrifying video taken from a truck parked about one kilometre from the impact site.

It showed the driver sitting calmly in the vehicle's cab moments before he's startled as the plane smashes into the ground.

The stunned man then jumps out and runs, shouting"oh, my God".

The plane with three people aboard crashed about 5.15pm on Tuesday (US Eastern Standard Time) as it was departing for Honolulu from Louisville Muhammad Ali International Airport. Video showed flames on the plane's left wing and a trail of smoke.

The crash had a ripple effect, striking and causing smaller explosions at Kentucky Petroleum Recycling and hitting Grade A Auto Parts, though it could have been worse, Beshear said.

"Thankfully, a local restaurant that is right there... was missed and now is helping the search and rescue," Beshear said.

"Another blessing is this plane could have potentially hit the major Ford factory or the convention centre, those are all close by, and did not."

University of Louisville Hospital said two people were in critical condition in the burn unit Wednesday and that 13 others had been treated and discharged. Five people were treated at other hospitals.

Beshear declared a state of emergency and mobilized the National Guard in an effort to quickly free up resources.