UPDATE: The winter weather might have played a role in a serious bus crash with students on board. A SUV collided with a school bus on Bee Branch Boulevard and Timberlinks Drive on Signal Mountain.

Police said Bus #60 was on its way to Signal Mountain Middle High School when the SUV collided with the bus head-on.

Bus #60 was carrying middle school students and only three miles from school when it was stopped by the oncoming vehicle.

"It had potential to be a whole lot worse, but luckily no one was injured severely," said Chief Mike Williams, with Signal Mountain Police Department.

The SUV was smashed in and the bus had some damage to the front end. More importantly, the driver is okay and so is the bus driver and the 13 students on board.

Chief Williams stopped short of saying what caused the crash, but said the SUV driver is likely at fault.

"The SUV was in the bus' lane, but what caused that, I have no idea," he said.

Temperatures dropped below freezing and black ice covered some back roads on Tuesday. School was delayed for two hours for the second day this week, but in this case, the roads weren't to blame. A spokesperson for Hamilton County School District said the driver's windshield was partially covered in frost at the time of the accident and might have played a role in the crash.

Chief Williams said the bus driver saw the oncoming car and brought the bus to a complete stop, which he believes reduced the impact for everyone involved.

"She wasn't traveling and enhancing the impact, it tore up the front end of the SUV pretty good and it would have been a whole lot worse if she hadn't stopped," Williams explained.

Traffic investigators with the Hamilton County Sheriff's Office are looking into what caused the driver to go into the wrong lane. The SUV driver could face lane violations and reckless endangerment charges.

Williams said drivers need to take extra time to defrost windshields and drive slow during these conditions.

"Use extra caution and be on the lookout for black ice because you're in it before you realize it many times," Williams said.

Signal Mountain police officers said in a separate situation, another Hamilton County school bus broke down Tuesday morning on the mountain. Students were transferred to another bus and brought to school.

Channel 3 records show this is the first major crash involving a school bus since 2013 on Signal Mountain. In that crash, 16 people were injured.

PREVIOUS STORY: A frosted window is the cause of a school bus crash Tuesday morning on Signal Mountain.

Hamilton County Schools spokesperson Tim Hensley tells Channel 3 that the SUV drifted into oncoming traffic. The bus driver noticed in enough time to stop the bus which lessened the impact of the crash.

The front window of the SUV was still partially covered in frost and ice from overnight. 

We'll continue to update this story. 

PREVIOUS STORY: A school bus and an SUV crashed in what appears to have been a head-on collision Tuesday morning on Signal Mountain. There were 13 middle school students aboard Bus #60 at the time.

A second bus was dispatched to transfer the students to take them to school.

The crash happened at Bee Branch Boulevard and Timberlinks Drive.

Hamilton County Board of Education spokesman Tim Hensley says there were no injuries reported on the bus.

Buses are running slightly behind schedule this morning, after a delayed start and some icy conditions on the roadway.