HARBIN, May 12 -- Construction work on a new exhibition hall of the notorious Unit 731 established by Japan in the northeast China city of Harbin has started, the publicity department of the Harbin Municipal Committee of the Communist Party of China announced on Monday.

Ni Yang, principal designer of the hall, said that the new exhibition hall consisting of ground-level and underground parts will be built on the ruins of Unit 731. Evidence of the crimes of Unit 731 will be displayed in the underground hall.

Unit 731 was a biological and chemical warfare research base established in Harbin in 1935 and the center of Japan's biological warfare in China and Southeast Asia during WWII. At least 3,000 people were killed in experiments there.

The construction area will cover around 15,000 square meters and will be mainly decorated in black, white and gray, Ni added.

The exhibition hall is expected to open to the public in 2015, according to the department.

It will take about two and a half hours to tour the new exhibition hall.

After the completion of the new hall, the former site of Unit 731 will be closed and put under protection as cultural relics, the department said.

A new park covering 80,000 square meters will also be built near the new hall.

As the world's largest ruins of a germ warfare research site, Unit 731 is of outstanding historical and educational value. The ruins of Unit 731 were included on China's tentative list of world cultural heritage sites in 2012.