There were high levels of smoke at the scene About 60 firefighters are tackling a blaze affecting two tour buses at the The O2 arena in south-east London.
A London Fire Brigade (LFB) spokesman said firefighters were called to the scene in Greenwich at 0818 GMT.
Ambulance crews have treated six people at the scene for smoke inhalation, a spokesman said.
A spokeswoman for The O2 said the venue had been evacuated and a decision on whether Tuesday’s Kings of Leon show would go ahead would be made later.
A spokesman for the LFB said the fire, which is now under control, was in a loading bay area and not in the seating or stage area.
He added both coaches had been completely burnt out.
LFB station manager Sally Cartwright, who is at the scene, said: “Our crews are doing a fantastic job, especially given the levels of smoke down here which has led to quite challenging conditions.”
A spokeswoman for The O2 said the fire started in a tour bus “related to tonight’s show” and spread to another tour bus in the loading bay.
She added: “Assessments are currently under way and we expect to make a decision in the next couple of hours as to whether tonight’s Kings of Leon show will go ahead.
“We will keep our website updated.”
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