Cairo -- Egypt says it has asked Interpol to help track down a 3,000-year-old sculpture of the famed boy pharaoh Tutankhamun after Christie's auctioned it off last week despite Cairo's objections. The Britain-based auction house sold the brown quartzite head depicting King Tut for more than 4.7 million pounds ($5.9 million).

Egypt's National Committee for Antiquities Repatriation says in a statement late Monday that it hired a British law firm to file a lawsuit against Christie's, saying the auction house did not provide documents proving ownership.

Christie's has denied any wrongdoing, saying it carried out "extensive due diligence" to verify the provenance of the statue and had "gone beyond what is required to assure legal title."

Laetitia Delaloye, head of antiquities of Christie's, poses for a photograph with an Egyptian brown quartzite head of the God Amen prior to its' sale at Christie's auction house in London, Britain, July 4, 2019. REUTERS

The committee also criticized British authorities for not supporting its claim to the sculpture.

Get Breaking News Delivered to Your Inbox

Laetitia Delaloye, head of antiquities at Christie's, told the Reuters news agency last week that it is "impossible to track them (ancient artifacts) back over the millennia of their existence, so what we endeavour to do is to research their modern history and in this case it actually brought us back to the 1960s when it was in an Austrian aristocratic collection."

She said she had gone over city archives in Germany "and found the trace of the head, and we were able to talk to the previous owners directly, which is very important for us. And when we carry (out) this extensive due diligence it's of course normal for a piece of this importance."

Delaloye said Christie's had been in contact with the Egyptian authorities in Cairo and at the Egyptian embassy in London "given them all the information that we have over the piece, because through this research, we're confident that the legal status of the piece and the title of ownership is clear."