The British Museum was alerted more than two years ago to the possible theft or disappearance of valuable artefacts when an art historian became suspicious about objects for sale on eBay.

But the museum’s director, Hartwig Fischer, said Friday that he didn’t treat the whistleblower’s warning seriously enough and announced his resignation as investigators figure out what happened to hundreds of missing pieces, including gold jewellery, semi-precious gems and antiquities dating to the 15th century BC.

“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,” Fischer said in a statement. “The responsibility for that failure must ultimately rest with the director.”

The museum fired a staff member more than a week ago and said legal action would be taken against that person. London’s Metropolitan Police are investigating and the museum has ordered an independent review of security as well as a ’’vigorous programme to recover the missing items.″

Most of the items were small items kept in a storeroom and none had been on display recently, the museum said.

The 264-year-old British Museum is a major London tourist attraction, drawing visitors from around the world. Its collection includes the Rosetta Stone that unlocked the language of ancient Egypt, scrolls bearing 12th-century Chinese poetry and masks created by the Indigenous people of Canada.

The museum has also attracted controversy because it has resisted calls from communities around the world to return items of historical significance that were acquired during the era of the British Empire. The most famous of these disputes include marble carvings from the Parthenon in Greece and the Benin bronzes from West Africa.

“We want to tell the British Museum that they cannot anymore say that Greek (cultural) heritage is more protected in the British Museum," Despina Koutsoumba, head of the Association of Greek Archaeologists, told the BBC this week.

Fischer’s announcement included an apology to the whistleblower, Ittai Gradel, a British-Danish art historian and dealer.

Gradel told The Associated Press he became suspicious after buying one of three objects a seller had listed on eBay. Gradel traced the two items he didn't buy to the museum. The object he bought wasn’t listed in the museum's catalogue, but he discovered it had been owned by a man who turned over his entire collection to the museum in 1814.

Gradel said he found the identity of the seller through PayPal and it was the person at the museum who has since been sacked. Gradel said that 69 other objects he bought from the same person were then “guilty by association.”

Gradel said that Fischer had done the right thing by stepping down and he accepted his apology. But he said Deputy Director Jonathan Williams should also resign, adding that Williams had assured him that a thorough investigation found no improprieties.

The museum said Friday that Williams would step aside during the independent review.

“He basically told me to sod off and mind my own business,” Gradel said. “It is beyond me how any responsible museum person could see this evidence without all alarm bells going off immediately."

On Wednesday, Fischer issued a statement saying that the museum had taken the allegations seriously in 2021. But he said concerns had only been raised about a small number of items and said it was frustrating to learn that Gradel, whom he did not name, had “many more items in his possession."

Gradel said it was an “outright lie” he withheld information from the museum and said it appeared that Fischer never read the documents he sent. He said he offered any assistance they needed and they never contacted him.

“I also misjudged the remarks I made earlier this week about Dr Gradel,” Fischer said Friday. “I wish to express my sincere regret and withdraw those remarks.”

Fischer, a German art historian, said he would leave as soon as a temporary leader could be appointed.

George Osborne, chair of the museum trustees, said the board accepted Fischer's resignation and that he acted “honourably in confronting the mistakes that have been made."

“I am clear about this: we are going to fix what has gone wrong,” Osborne said. “The museum has a mission that lasts across generations. We will learn, restore confidence and deserve to be admired once again.”

The museum had said it would take legal action against the dismissed staff member.