According to the local authority, the school van carrying 15 kindergartners and one teacher plunged into a roadside pond around 9 a.m. in a rural area of Guixi City, which is located in the city of Yingtan.
Three children died instantly. Another eight died at a local hospital after efforts to save them failed.
Four other children were injured and are in stable condition, the local authority said.
The authority also disclosed a list of casualties.
The latest investigation results show that the children, aged 4 to 6, were students of a privately-run kindergarten. The school's principal, 35-year-old Zhou Chun'e, was driving the van.
Police said Zhou overloaded the vehicle, which had a designed seating capacity of seven, and "drove improperly," causing the accident.
According to the ministry circular, recent school attacks and accidents which have caused students' injuries and deaths have shocked people.
11 Chinese children dead after van plunges into pond