US federal safety investigators have located the "black box" recorders from the wreckage of a UPS cargo plane that crashed in flames on takeoff from the airport at Louisville, Kentucky, killing at least 12 people, officials said on Wednesday.

Todd Inman, a member of the National Transportation Safety Board, also confirmed that a large "plume of fire" erupted around the plane's left wing and that one of its three engines detached from that wing as the wide-body jet was rolling down the runway.

The 34-year-old MD-11 freighter was bound for Honolulu with three crew members aboard when it crashed just after clearing a fence at the end of the runway during takeoff on Tuesday evening, striking a number of structures just beyond airport property, Inman said.

The plane was immediately engulfed in a fireball, igniting a string of blazes and scattering a debris field that stretched about 800 metres through an industrial corridor, including a petroleum recycling facility that was set ablaze and exploded.

The crash and ensuing fires also forced a shutdown of the airport for the night and disrupted airport-based operations at the UPS Worldport facility, the company's global cargo hub for its air shipments worldwide, slowing delivery services.

Inman, in the first NTSB briefing since the disaster, said the flight data recorder and cockpit voice recorder were built to withstand crash impacts and intense heat from fires and they appeared to be intact when located on Wednesday amid the crash debris.

"We feel comfortable that once we get these to our lab in (Washington) DC that we will be able to get a good readout of the applicable data, and that will be yet another point of information that will really help us understand what happened," Inman told reporters.

The NTSB typically issues preliminary reports into major air crashes within 30 days, but it takes 12 to 24 months to complete a full investigation, make a finding of probable cause and issue recommendations to help avoid similar incidents.

Earlier on Wednesday, Governor Andy Beshear declared a state of emergency in Kentucky aimed at hastening the flow of disaster response resources to the scene of the crash.

As of Wednesday evening, at least nine people were confirmed to have been killed on the ground, in addition to the three members of the plane's crew who perished, according to authorities.

"I’m deeply saddened to share that the death toll has risen to 12, with several individuals still unaccounted for," Louisville Mayor Craig Greenberg said on social media platform X as recovery teams continued to pick through the crash zone. (Reuters)