Six children have died after a school bus crashed into a tree in Chattanooga, Tennessee, on Monday, according to police.

The bus was carrying 37 Woodmore Elementary School students, of kindergarten to fifth grade school-age, usually between the ages of five and eleven, when the accident occurred, causing the vehicle to split in two and turn on its side.

The driver, Johnthony Walker, has been arrested and charged with five counts of vehicular homicide, reckless endangerment and reckless driving, according to Chattanooga Police Chief Fred Fletcher.

Police confirmed authorities were called just before 3:30 pm yesterday, and Chattanooga Fire Department worked for "many hours" to remove all the children from the bus.

Of the students involved in the crash there were five confirmed fatalities, six critically injured, six admitted to hospitals but not critically injured and 20 treated and released by local hospitals.

"Certainly, speed is being investigated very, very strongly as a factor in this crash," Mr Fletcher said.

“A warrant has been issued to remove the informational box on the school bus and review the video."

Police confirmed families of the victims had been notified and authorities were working to reunite all surviving children with their families on Monday night.

"Taking care of the children that are injured is our number one priority. Taking care of the families who are looking for, caring for and grieving for children is our second priority," Mr Fletcher said.

"Our thoughts, our prayers and all of our efforts are with the families of these children and others impacted by this tragedy."

The National Transportation Safety Board said it would send a team to Chattanooga early Tuesday, according to a tweet from the federal agency's account.

At the scene, parents were heard crying and screaming "that's my baby" as they arrived, according to CNN-affiliate WTVC.