British Museum director Hartwig Fischer resigned on Friday, admitting the museum did not act “as it should have” on warnings that items had gone missing.
The museum in central London is best known for housing collections that include the Rosetta Stone and the Parthenon Marbles.
It said last week it had dismissed a staff member and alerted the police after artefacts from its collection were found to be “missing, stolen or damaged”.
The items included gold jewellery and gems of semi-precious stones and glass dating from 15th century BC to the 19th century, it said in a statement.
London’s Met police said on Thursday a man had been interviewed by investigating officers, although no arrests had been made.
Fischer, a German art historian, said he would step down with immediate effect because of lapses in procedures that allowed the items to be taken.
“The responsibility for that failure must ultimately rest with the director,” he said.
“It is evident that the British Museum did not respond as comprehensively as it should have in response to the warnings in 2021, and to the problem that has now fully emerged,” he added.
Emails leaked to the BBC claimed the museum was alerted by an antiquities dealer to items being sold on eBay in 2021 and ignored the report.
Most of the items affected were described by the museum as “small pieces kept in a storeroom belonging to one of the museum’s collections”.
None had been on recent public display and they were kept mainly for academic and research purposes, it said earlier, without elaborating.
Before his resignation, Fischer said security had been tightened and outside experts had been brought in to help compile a “definitive account” of what was missing, damaged or stolen.
“This will allow us to throw our efforts into the recovery of objects,” he said.
George Osborne, chairman of the British Museum, said its trustees were “extremely concerned when we learnt earlier this year that items of the collection had been stolen”.
He said the priority was to recover the items, find out what could have been done to prevent the theft, and “do whatever it takes, with investment in security and collection records, to make sure this doesn’t happen again”.
Founded in 1753, the British Museum is one of the most famous galleries in the world, with a collection of around eight million objects, including ancient artefacts such as Egyptian mummies.
But in recent years the museum has faced increasing pressure to address the contested items in its collection, which were acquired during the era of the British Empire.
This includes one of the museum’s prized exhibits, the Parthenon Marbles, also known as the Elgin Marbles, which Greece insists should be returned.
The sculptures were taken from the Parthenon temple in Athens in the early 19th century by British diplomat Lord Elgin and have been held by the British Museum ever since.