CHATTANOOGA, TENN. - Update on Nov. 22: Hamilton County Superintendent Kirk Kelly confirmed Tuesday morning that five students were killed in a school bus crash.

Kelly said three of the students were fourth graders, one in kindergarten and one in first grade. In total, four girls and one boy were killed.

"We're going to do anything that we can to remember these students and support them," Kelly said. "They will always be with us throughout our lives."

Twelve students remain in the hospital as of Tuesday morning, including six in the Intensive Care Unit, according to Kelly.

Hamilton County District Attorney Neal Pinkston said earlier Monday there were six fatalities, which included five deaths at the scene and one at the hospital.

A total of 37 students were on board during the 3:30 p.m. ET crash on Monday, according to Kelly.

Kelly did not provide information on Tuesday morning on the students killed in the crash out of respect for the families involved.

On Tuesday morning, Kelly also did not provide much information on bus driver Johnthony Walker’s work history. Kelly did confirm Walker worked as an employee at Durham Bus Services.

Walker, 24, is charged with five counts of vehicular homicide, reckless endangerment and reckless driving, according to police.

Chattanooga Mayor Andy Berke also spoke at Tuesday morning's news conference in front of Woodmore Elementary School.

"Five is a cursed number in our city right now," Berke said.

Five Chattanooga servicemen were killed in a shooting by a lone terrorist on July 16, 2015.

The National Transportation Safety Board said on Tuesday morning that it is launching an investigation of the crash, and a team of federal investigators will deploy to Chattanooga.

NTSB Chairman Christopher Hart said the investigation should take between seven and 10 days.

Hart said the NTSB will look to see on the status of data recorders on the bus, and to see if the bus had security cameras.

Previous Story on Nov. 21: The bus driver in a fatal school bus crash in Chattanooga Monday has been arrested and charged with five counts of vehicular homicide, reckless driving and reckless endangerment, Chattanooga Police Chief Fred Fletcher said late Monday night.

Fletcher identified the driver as 24-year-old Johnthony Walker.

The police chief said more charges may be added as the case proceeds to a Hamilton County grand jury.

"This is an absolute nightmare for our community, for police, for partners, but I can ensure you we are prepared and trained to make sure this is investigated thoroughly and we're making sure we have all the resources families, the schools and the communities need to respond to this tragedy and trauma of this grieving loss," Fletcher said.