The museum says that an independent investigation into security has been requested and a “vigorous program” has been launched to find the missing items.
It concerns gold jewelery and stones of semi-precious stones and glass dating from the 15th century BC to the 19th century.
“Our priority now is threefold: first, recovering the stolen items; second, find out what could have been done to prevent this; and third, do whatever it takes, with investment in security and collection management, to make sure this doesn’t happen again,” said George Osborne, President of the British Museum.
The museum says legal action will be taken against the person in question and that the case is being investigated by the London police.