CHATTANOOGA, Tenn. — A school bus driver has been arrested after five students were killed and dozens were injured in a single-vehicle crash here on Monday afternoon.

Chattanooga Police Chief Fred Fletcher said in a press briefing that the school bus, which was transporting 37 elementary students, left the roadway and struck a tree. He said that the bus was the only vehicle involved in the crash, which occurred in clear and dry conditions.

Images from the scene show the school bus on its side with the tree pressed into the roof.

Fletcher said that fire department and EMS personnel “worked for many hours using a number of specialized tools, strategies, and tactics to rescue and remove children” from the bus.

The Chattanooga Police Department has confirmed that five students on the bus have died, six were critically injured, another six were admitted to hospitals but were not critically injured, and 20 were treated and released by local hospitals.

After the crash, investigators interviewed the school bus driver, 24-year-old Johnthony Walker. He was subsequently arrested and charged with five counts of vehicular homicide, reckless endangerment, and reckless driving. Fletcher said that additional charges may be added.

Local investigators were continuing to process evidence from the scene overnight. Fletcher said that a warrant had been issued to remove the black box data recorder from the school bus and to review video surveillance camera footage from the bus.

The police chief said that more details about the circumstances of the crash would be released in a later update, but he noted that the speed of the school bus was one of the focal points of the investigation.

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

The police chief added that the families of all of the children who were killed had been notified.

“Our thoughts and prayers are with their families, their schools, their friends, and our entire community impacted by this tragedy,” Fletcher said.

The National Transportation Safety Board (NTSB) also sent a team to investigate the Chattanooga crash. NTSB Chairman Christopher Hart said in a press briefing that his agency will work to determine the cause of the crash and to develop recommendations “to try to prevent this from happening again.”

Hart said that he didn’t know whether the bus had seat belts. Like most states, Tennessee does not require seat belts on school buses.

The Hamilton County Department of Education said that the 37 students on the bus attend Woodmore Elementary School. A fund has been set up at the Community Foundation of Greater Chattanooga to help those impacted by the crash. Donations can be made here.

“We at Hamilton County Schools ask you also keep the Woodmore Elementary School community in your thoughts and prayers during this difficult time,” the district said in a statement.