Trustees at the British Museum have launched an independent security review after precious items, some dating back to the 15th century BC, were found to be missing, stolen or damaged.
A member of staff has been dismissed and the museum said it would be taking legal action against the individual, the charity said in a statement.
The majority of the items in question were small pieces – mainly gold jewellery and gems of semi-precious stones and glass – were kept in a storeroom belonging to one of the museum’s collections, it said.
Separately, the matter is also under investigation by the Economic Crime Command of the Metropolitan Police.
An independent review will be led by former trustee Sir Nigel Boardman and Lucy D’Orsi, chief constable of the British Transport Police.
They will look into the matter and provide recommendations regarding future security arrangements at the museum, the charity said.
They will also “kickstart – and support – a vigorous programme to recover the missing items”.
George Osborne, the former Conservative Chancellor who is chair of the British Museum, said: “The trustees of the British Museum were extremely concerned when we learnt earlier this year that items of the collection had been stolen.
“The trustees have taken decisive action to deal with the situation, working with the team at the museum.
“We called in the police, imposed emergency measures to increase security, set up an independent review into what happened and lessons to learn and used all the disciplinary powers available to us to deal with the individual we believe to be responsible.
“Our priority is now threefold: first, to recover the stolen items; second, to find out what, if anything, could have been done to stop this; and third, to do whatever it takes, with investment in security and collection records, to make sure this doesn’t happen again.
Hartwig Fischer, director of the British Museum, said: “This is a highly unusual incident. I know I speak for all colleagues when I say that we take the safeguarding of all the items in our care extremely seriously.
“The museum apologises for what has happened, but we have now brought an end to this – and we are determined to put things right.
“We have already tightened our security arrangements and we are working alongside outside experts to complete a definitive account of what is missing, damaged and stolen. This will allow us to throw our efforts into the recovery of objects.”