Chattanooga Fire Department assistant chief Tracy Arnold confirmed "multiple" children were killed in Monday's bus crash on Talley Road.

Speaking to media outside Woodmore Elementary School just after 6 p.m., Arnold could not immediately confirm the names or ages of those who were killed. The bus carried 35 students.

At least 23 students were taken to hospitals after the bus ran into a utility pole and overturned.

While emergency responders filled several blocks of Talley Road, officials from all levels of local government rushed to the scene.

A few minutes after 5 p.m., police chief Fred Fletcher called the matter "every public safety professional's worst nightmare."

"Our hearts go out, as well as the heart's of all the people around me, to the family, the neighborhood, the school and all the people involved in this," he said, with city and county officials at his side. "We assure you we're doing everything we can to help everybody be as safe as they can, get the care they need and get the support they need."

The rescue effort continued until after dark. Scenes from near the crash painted a grim picture.

Two bloodied students laid on stretchers in a front yard nearly an hour after the crash receiving attention from first responders.

Others who weren't rushed to the hospital walked away clutching their parents' hands, looking dazed with cuts on their faces.

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Children's Hospital at Erlanger says is it treating patients and working with the families.

"We will provide more information as soon as it is available," according to a news release from the hospital.

Angel Emergency Services Disaster Response Team bus pulled up to the emergency entrance. Erlanger employees pulled dark blue curtains over the emergency entrance to block bystanders' view.

Security staffers asked reporters to leave Erlanger property and stand on the sidewalk across the street. An announcement was made over the hospital public address system that the hospital was in a code triage.

The Chattanooga Fire Department says the last patient has been removed from the bus. 

A group a people who appear to be parents has gathered in the lobby of T.C. Thompson Children's Hospital at Erlanger.  Media was removed the lobby. 

Gov. Bill Haslam commented on today's crash:

"We've had a tragic event involving a school bus down in Hamilton County. We're going to do everything we can to assist in any way. It's a sad situation anytime there's a school bus with children involved, which there is in this case. We will do everything we can to assist in what I think is going to be a very sad situation."

A message sent to parents in Hamilton County tonight said: "We just wanted to inform you that Hamilton County schools faced a great tragedy today. School and county personnel are on scene of a bus accident on Tally Road in Chattanooga.  Extra counselors and support staff will be on hand to help students process this horrible incident."

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Emergency officials are on the scene of a Woodmore Elementary School bus accident in the Brainerd area.

The portion of Talley Road immediately north of its intersection with Brainerd Road is closed to traffic. A police officer in the area did not immediately disclose the severity of the incident, but a neighborhood resident said the bus hit a power line. Some homes in the area are without power, she said.

Police have established an extensive investigation scene, with yellow crime tape spanning several blocks. Ambulances, fire trucks and other law enforcement vehicles are dotting the street, and at least two children were still receiving medical treatment at the scene, as of 4:20 p.m.

The Chattanooga Fire Department described the crash as "very serious" in a tweet. 

This is a developing story.