Jiang Xulian, 39, from China, confessed to stealing the gemstone, worth 10 million baht or about $280,000 on Friday after it showed up on an X-ray scan, police said.

Jiang and her companion, a Chinese man, were detained at Bangkok's Suvarnabhumi International Airport last Thursday while trying to leave the country, said Maj. Gen. Sanit Mahathavorn, the police official overseeing the investigation.

An exhibitor at the 56th Bangkok Gems & Jewelry Fair had reported the diamond missing. The pair is believed to have switched the stone with a fake diamond after asking to inspect it.

After she was taken into custody, Jiang refused to eat any food and only drank water, police said.

She was given laxatives but three days later had still failed to pass the diamond. By this time, the stone had moved from her stomach to her large intestine.

Doctors then used a coloscope to extract the gem successfully on Sunday afternoon.

Jiang is being detained on a charge of theft and could face a three year jail sentence and a fine.

Diamond thieves who resort to swallowing precious stones are not unheard of.

In 2012, South African police arrested a man trying to leave the country who had swallowed 220 polished diamonds. The diamonds, worth an estimated $2.3 million, were discovered by an airport security body scanner.