CHICAGO - A US flight was evacuated prior to takeoff when a passenger's Galaxy Note 7 -- reportedly a replacement in Samsung's global recall -- caught fire, landing the company in new controversy.

Samsung has been struggling with a recall of 2.5 million Galaxy Note 7 handsets due to complaints of exploding batteries, a problem the replacement phones are supposed to fix.

But on Wednesday, a Southwest Airlines flight leaving Louisville, Kentucky was evacuated after a passenger's new Samsung phone began emitting smoke.

Brian Green, the owner, told tech news website The Verge that the phone was a replacement, which he picked up on September 21. He also provided a picture of its box, which has a black square symbol indicating that it was a replacement.

Some 60 percent of US consumers had swapped their devices for replacements by the end of last month.

The Verge reported Green had powered down the phone for takeoff, an account The New York Times confirmed through other eyewitnesses.

The heat damage from the apparent explosion was so severe that a fire official could not independently verify the model of the phone, according to ABC News.

"Until we are able to retrieve the device, we cannot confirm that this incident involves the new Note7," Samsung said in a statement.

"We are working with the authorities and Southwest now to recover the device and confirm the cause," the company added. "Once we have examined the device we will have more information to share."

The unprecedented recall, the first involving Samsung's flagship smartphone, has struck a blow to the reputation of the South Korean electronics giant, the world's largest smartphone maker.

With ever-fiercer competition, Samsung is desperate to avoid a full-blown disaster that could hammer its reputation.

Meanwhile the recall could cost the firm $3 billion in the long run, some analysts say.

"The continued news reports about the Note 7 aren't good for Samsung, especially for its brand reputation," Park Kang-ho, an analyst at Daishin Securities Co. told Bloomberg.

"If the noise continues even as phones are replaced, consumers will start raising doubts over the next Galaxy S model, so the faster Samsung settles things the better for its business."

Southwest Airlines said in a statement that all customers and crew "deplaned calmly and safely via the main cabin door."