BEIJING, Aug. 18 -- Historical documents released Tuesday showed people in service of the Japanese army in Shanghai city abducted and sold Chinese woman to serve as sexual slaves during World War II.

In April 1938, pro-Japanese elements in service of the Japanese army lured and trafficked Chinese women to hotels in Hongkou District in Shanghai and then sold them to the Japanese Army to work as "comfort women," according to the 1938 crime investigation records of the Shanghai International Settlement Police Station.

Four of the criminals were sentenced by the courts and two of the main criminals behind the trafficking hid in the area occupied by the Japanese Army, so they were not arrested, according to the records.

Tuesday's release by China's State Archives Administration (SAA), is the fourth episode of an eight-part series of videos and archives documenting the suffering of sex slaves at the hand of the Japanese military over 70 years ago.

The series of documents are available at the SAA's website.