DALLAS, Dhu-AlHijjah 8, 1436, Sep 22, 2015, SPA -- Chinese authorities have held a Texas businesswoman in custody for six months on allegations that she's a spy who stole state secrets, AP cited the woman's husband as saying on Tuesday. Phan Phan-Gillis, 55, was part of a trade delegation when she was detained at a border checkpoint in March. Her husband, Jeff Gillis, is asking President Barack Obama and the State Department to arrange the release of his wife, who was part of a trade delegation when she was detained at a border checkpoint in March. He denies the accusations. The Chinese Foreign Ministry has said Phan-Gillis is being investigated on suspicion of threatening China's national security. Although she has not been charged, she was formally arrested over the weekend and moved to a more secure detention facility in the southern city of Nanning, according to her husband, who said the arrest allows Chinese authorities to continue their espionage investigation. His wife has been visited six times by American consular officers since her March 20 arrest, according to the State Department, which said it was closely monitoring the case. Phan-Gillis, known as Sandy to family and friends, is a Vietnamese-American of Chinese descent who has lived in Houston for about 30 years. -- SPA 22:35 LOCAL TIME 19:35 GMT www.spa.gov.sa/w