The British Museum says it's taking legal action and the Metropolitan Police's economic and crime command is investigating.
The British Museum staff member sacked after the disappearance of a number of artefacts has been named as Peter Higgs.
Higgs, an expert on Greek and Mediterranean artefacts, had been with the British Museum for almost three decades and was its curator of Mediterranean cultures.
Higgs was allegedly dismissed earlier this year after the museum realised that gold jewellery, semi-precious stones and glass dating from the 15th century BC to the 19th century AD were missing, stolen or damaged.
The museum said it will be taking legal action and the Metropolitan Police's economic and crime command is investigating.
Higgs' son, Greg, denied his father had done anything wrong.
"He's not happy about it at all," Greg Higgs told British newspaper the Telegraph.
"He's lost his job and his reputation and I don't think it was fair. It couldn't have been (him). I don't think there is even anything missing as far as I'm aware."
His father had “lost all faith in the museum”, he added.
A spokesperson for the British Museum said they could not comment because of the police investigation.