/ Updated 
By Chris Fuchs

More than a year after she was first detained in China, the Chinese government has charged an American business woman from Houston, Texas, with spying, according to published reports.

Sandy Phan-Gillis, a naturalized U.S. citizen of Chinese descent, was placed under residential surveillance last March after trying to cross to Macau from the southern coastal city of Zhuhai on a trade delegation, according to the UN Working Group on Arbitrary Detention. Chinese authorities approved her arrest on Oct. 26, 2015, the group said.

Sandy Phan-Gillissavesandy.org

"Based on our understanding, Phan-Gillis, because of her suspected crimes of espionage, has been charged according to law by the relevant Chinese department," Chinese Foreign Ministry spokeswoman Hua Chunying told reporters at a regular briefing Tuesday, according to Reuters.

Phan-Gillis’ husband, Jeff, told The New York Times the indictment alleged his wife spied in 1996 during a visit to Guangxi in southern China, but added that his wife’s passport shows she wasn’t even in China during that year, according to Reuters.

Her husband also said Phan-Gillis, 56, was accused of attempting to recruit Chinese in the U.S. to work for a “foreign spy organization,” a charge he said was false, according to The Times.

The U.S. State Department said it was “deeply concerned” over Phan-Gillis’ welfare and has pushed Beijing for more details about her case, Reuters and The Times reported.

The UN Working Group on Arbitrary Detention has also called for Phan-Gillis’ release, a recommendation the State Department said “we would encourage the Government of China to review and consider,” spokesman John Kirby told reporters at a July 6 daily press briefing.

The U.S. consulate in Guangzhou, China, has visited monthly with Phan-Gillis since she was detained on March 20, 2015, and has provided her with consular assistance, Kirby said during the July 6 briefing.

RELATED: China Detains Houston's Sandy Phan-Gillis on Spying Allegations

Attempts by NBC News to reach Jeff Gillis and Sandy Phan-Gillis' attorneys for comment were not immediately successful.

News of the espionage charges against Phan-Gillis comes as President Barack Obama heads to China for a G20 Summit. He is slated to meet with Chinese President Xi Jinping on Saturday for bilateral talks

Jeff Gillis, who spoke publicly about his wife’s detainment last September, told the Times this week that “the time really is critical for Sandy” with the meeting of the U.S. and Chinese presidents.

Tensions have been building between the two countries, resulting from China’s territorial claims in the South China Sea and accusations against the Chinese of cyber espionage.

In July, Chinese businessman Su Bin, 51, was sentenced to nearly four years in prison for helping military officers in China hack into the computer networks of United States defense contractors and steal sensitive technical data, prosecutors said.

If Phan-Gillis is convicted of the espionage charges, she could face up to more than 10 years in a Chinese prison, her husband said, according to The Times.

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