BEIJING - China's Ministry of Public Security on Thursday vowed efficient investigation of the case of the "house sister," a woman found to have illegally amassed 20 homes using multiple identities.

The ministry set up a special team to supervise an investigation into how Gong Aiai, who has at least two identities and "hukou", Chinese household registration records, had been allowed to possess over 20 houses worth a total of about 1 billion yuan ($159 million).

China's property market controls restrict individuals buying multiple homes, but "ghost" identities can help householders skirt the restrictions.

Gong's identity duplicates also raised public concerns of possible corruption such as unfair distribution of government-subsidized affordable housing and officials' evasion of personal property supervision.

Gong's huge wealth was first exposed by a microblogger online and soon sparked a new round of public anger over administrative power abuses and oversight.

According to a statement issued by the ministry, Gong first registered as a resident in the town of Shenmu in Northwest China's Shaanxi province, and later registered three identities respectively in two counties in the neighboring Shanxi province and Beijing between 2004 and 2008.

One of the fake identities was revoked in January 2012, the statement said.

The ministry promised a thorough probe and serious punishment for implicated law violators, and called for a streamlining of the household registration and identity issuing system to make similar offenses less likely in future.