XI'AN - A woman, known as "house sister," suspected of owning multiple properties with forged identities has been detained by police, authorities in Northwest China's Shaanxi province said Tuesday.

Gong Aiai, former deputy head of the Shenmu County Rural Commercial Bank, in Yulin city, was detained on Monday for forging official documents and government stamps. A spokesman with the Shenmu County Government said she was in police custody in Yulin city.

Gong was confirmed to have four hukou, a household registration record which should be unique for each Chinese citizen. The three fake ones, two in Shaanxi province and the other in Beijing, have been revoked, said the spokesman.

So far, at least seven people, including four police officers, have been detained for helping forge hukou for Gong.

Last month, online whistleblowers revealed that Gong, later nicknamed "house sister," had accumulated more than 20 properties worth an estimated 1 billion yuan ($159 million) in Beijing using fake IDs naming her as Gong Aiai and Gong Xianxia.

More properties were revealed later in Beijing and other places, such as Shenmu.

Investigations found that Gong, a contracted employee with the bank, had quit her position as deputy head in June 2012 to run her family business. The board approved her resignation request on January 2, 2013.

A further investigation is under way.