UPDATE: The National Transportation Safety Board's Go Team arrvived in Chattanooga Tuesday morning to begin their investigative work.

The team will determine what factors led to the crash, and will utilize the bus' "black box" and on-board camera to gather additional information.

The NTSB is expected to have a news conference later Tuesday.

PREVIOUS STORY: A school bus crash Monday afternoon claimed the lives of five children and injured more than 20 others. Four of the victims were girls; the other a boy.

Hamilton County Schools Interim Superintendent Dr. Kirk Kelly confirmed the tragic news at a 7:00am news conference Tuesday.

Three of the children were fourth graders, one a first-grader and another in kindergarten.          

School bus driver Johnthony Walker, 24, has been charged with five counts of vehicular homicide. He has also been charged with reckless endangerment and reckless driving, Chattanooga police said late Monday.

"Through our channels we can confirm there are children deceased," said a spokesperson for the Tennessee Highway patrol.

Officials earlier Monday said six children died, but Chattanooga Police Chief Fred Fletcher said late Monday that number was five.

The crash, which happened about 3:20pm on Talley Road, ended with the school bus turned over on its side, with the roof caved in. The bus was the only vehicle involved in the crash.

Thirty-seven Woodmore Elementary School students were aboard the bus when it crashed, twelve students are in the hospital for treatment; six of those are in intensive care.

Monday afternoon, first responders swarmed to the scene, as did school, city and county officials.

Fletcher described the accident as a "single-driver incident." The Chattanooga Fire Department tweeted photos of the accident that appeared to show that the bus flipped over after it struck a tree.

Tuesday morning, the National Transportation Safety Board said they would send  a 'Go Team' to Chattanooga to investigate the crash.

The NTSB will team will be led by Robert Accetta, who will serve as the investigator in charge.

The team will be looking at factors of the crash, such as human performance, road conditions, motor carrier operations and vehicle factors.

Investigators will now look at the vehicle's black box, which contains a camera. Police want to review the footage on it.

More information from the NTSB is expected later today.

NBC News and the Associated Press contributed to this report.