The road where a school bus crashed killing five children on Monday was not on the designated route for the school bus driver to take, according to the National Transportation Safety Board.

NTSB Chairman Christopher Hart said in a press conference Wednesday that Talley Road was not on the designated route for the school bus, and the federal agency will be looking at why the driver was on that road.

No drugs or alcohol were found in the system of the school bus driver at the wheel in a crash that killed five children and injured several others, according to Chattanooga police.

Johnthony Walker, 24, of Chattanooga was charged with five counts of vehicular homicide, reckless endangerment, and reckless driving after the Monday crash. Investigators said he was driving "well above" the posted speed limit of 30 m.p.h. when the crash happened.

MORE: Remembering the victims of the bus crash

There were 37 young children on the bus. Four girls and one boy from Woodmore Elementary School died. Six students remained in the hospital as of Wednesday afternoon, with five of them in critical condition.

Johnthony Walker, 24, school bus driver involved in fatal Chattanooga crash. 

There are two separate investigations ongoing--- a criminal investigation and a federal investigation by the National Transportation Safety Board (NTSB) to determine how it happened.

At a press conference on Wednesday, Sgt. Austin Garrett of the Chattanooga Police Department said they are still in the early stages of their investigation. They are reviewing video from cameras on board the bus, and are obtaining warrants to get the data devices on the bus.

They have determined that none of the victims were ejected from the bus during the crash.

They are also working to interview the children, but it is very delicate because of their age and the traumatic experience. They are coordinating the interviews with people who are specially trained to deal with children in these circumstances. They did address one report by one mother that the bus driver asked the children if they were prepared to die before the crash. None of the other witnesses they've spoken to have repeated that information.

Sgt. Garrett also said they've heard reports of complaints against the driver, but have not been able to corroborate those.

When asked if Walker was still cooperating with the investigation, Garrett declined to comment.