OAKLAND, Iowa — A school bus driver and a student here were killed in a blaze on their bus on Tuesday morning.

Lt. Rob Ambrose of the Pottawattamie County Sheriff's Office told School Bus Fleet that the driver and the student were the only occupants of the bus at the time.

Max Christensen, state pupil transportation director for the Iowa Department of Education, told SBF that the school bus was operated by Riverside Community School District, which has a fleet of about 17 buses.

The incident occurred in a rural area east of the small town of Oakland, which is in southwestern Iowa near the border with Nebraska. The school bus driver was picking up the student at a farm.

Ambrose said that the bus driver had apparently backed into a roadside ditch when the fire broke out at the rear of the bus.

The bus became engulfed in flames, and the driver and the student died in the fire, authorities confirmed. It is not clear at this point why they were not able to evacuate from the bus.

"That is still under investigation," Ambrose said. "We haven’t determined that, but it is believed that they could not get out the door normally used [the front door]."

The student’s mother called 911. Deputies were dispatched at 7:02 a.m., and the first deputy arrived at the scene at 7:15 a.m., Ambrose said. Firefighters also responded to the scene.

“Upon arrival, deputies from the Sheriff’s Office and firefighters from Oakland and Carson found the bus to be completely involved,” Chief Deputy John Reynolds said in a press release. “Once the fire was contained, the remains of two individuals were found on the bus.”

The Pottawattamie County Sheriff's Office identified the victims as school bus driver Donald Hendricks, 74, and student Megan Klindt, 16.

Ambrose told SBF that he did not yet have information about the school bus, such as the age and make. Based on a photo from the Omaha World-Herald, the bus appears to be an older Type C conventional model. It was not yet clear how many emergency exits the bus was equipped with.

Christensen, the state director, said that the incident was heartbreaking, especially considering the timing.

“It’s a tragic event no matter what time of year it happens, but being so close to Christmas makes it all the more tragic,” he said. “My thoughts and prayers are with the families.”

The incident remains under investigation by local authorities. Also, the National Transportation Safety Board has launched a full team investigation, SBF has learned.

Dr. Timothy Mitchell, superintendent of Riverside Community School District, said in a statement on the district website that schools were in session on Tuesday. A crisis team, school counselors, and volunteers were deployed to all of the district's schools to support students and staff.

"This morning, the Riverside Community School District suffered a tragedy when we lost a student and an employee in a school bus accident," Mitchell said. "Our hearts go out to their families and loved ones."

The superintendent added that the district is cooperating with law enforcement in the investigation of the incident.

"The safety of students and staff is the top priority for the district," Mitchell said.