Hundreds of people were evacuated from the Science Museum in London
Three fire engines were called to the popular attraction in Kensington, west London – attracts millions of visitors every year – at 4:02pm.
Around 400 people were evacuated from the museum as London Fire Brigade (LFB) investigated the cause of the fire alert.
A spokesman said the museum was placed on lockdown as a "precaution" and would re-open "when it was safe to do so".
Pictures from the scene showed huge crowds gathered outside the museum, which was packed out with schoolchildren on half-term.
Twitter user Rob Swan wrote: "Just been evacuated from Science Museum London due to 'an incident' – no idea what's going on yet."
LFB said the museum's fire alarms were triggered when a faulty extractor motor set alight.
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