BBC Look East was forced off-the-air after the Forum in Norwich, where it is filmed, had to be evacuated after the fire alarm sounded.
Visitors and staff were escorted out at 6.40pm and the broadcast cut to the BBC24 service which was airing Sports Day.
Forum staff returned to the building at 6.50pm but the BBC Look East broadcast did not return as the One Show followed at 7.00pm.
The fire alarm was caused by a faulty fire sensor that had tripped the system.
Viewers took to Twitter in confusion.
One viewer said: 'As Delia once said, where are you? BBC News24 on BBC1 instead of look east.'
BBC Look East eventually took to Twitter to say: 'Sorry about the short Look East tonight – we had to evacuate our building due to a fire alarm. We'll be back at 20.00 on BBC One East.'
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