ERLANGER, Tenn. – Six children from the Chattanooga bus crash remain at Children’s Hospital, dropping from 12 on Monday.

Currently, there are five children listed in critical condition at Children’s Hospital. All six children who were on patient floors at the hospital have been discharged, and one child was transferred from an intensive care unit to a regular hospital room.

On Monday, 19 other crash victims were treated and released within two hours of arriving at Children’s Hospital. Dozens of balloons, cards, stuffed animals and candles have been left at the bus accident scene.

Photos | Memorial for Chattanooga school bus crash victims

The bus had just left Woodmore Elementary carrying 37 students, and had not yet dropped off any students along its route when the crash happened around 3:30 p.m.

Four girls and one boy from Woodmore Elementary School died, Hamilton County Interim Superintendent Kirk Kelly confirmed.

Photos | Fatal school bus crash in Chattanooga

Johnthony Walker, 24, of Chattanooga, was arrested on five counts of vehicular homicide, reckless endangerment and reckless driving.

Police: Bus driver going 'well above' speed limit before deadly crash

Police determined Walker was driving at a high speed on the narrow, winding Talley Road, based on witness statements and physical evidence.

"The posted speed limit around the crash was 30 mph with lower advisory speeds on the curves," Christopher Hart, chairman of the NTSB, said.

The bus did not have seat belts. Hart said it was too soon to know if seat belts would have made a difference in the crash.

Hart said the NTSB investigators will be looking at "the totality of the situation" to determine not only what happened in the crash, but why.

"We will determine what caused this accident and we will make recommendations to try to prevent it from happening again," Hart said.

How you can help support Chattanooga bus crash victim