Hall County school buses ground to a halt Thursday morning after an unexpected layer of ice formed on streets.

School officials, concerned about reports of deteriorating road conditions, decided about 7:15 a.m. that drivers needed to "pull off their routes into a safe area," Hall County spokesman Gordon Higgins said.

The delay lasted about 40 minutes and heaters in the buses kept children warm, he added.

The district's decision generated strong reactions from parents.

Flowery Branch resident Leslie Channell said she was driving her three sons to school when the roadways started to become slick.

"I almost wrecked coming out of the high school on my way to the middle school," Channell said. "I think they needed to at least delay the school. It's not worth putting the kids at risk."

Higgins said school officials, following procedure in inclement weather, checked conditions earlier in the morning and determined "roads were absolutely clear."

"Shortly thereafter, the temperature dropped and we had icing," he said.

Some parents said school officials were in a tough predicament.

"The roads were fine at 6," wrote Richard Taylor on The Times' Facebook page. "The buses had already begun their routes and then the weather changed. That's what happens!"

Others lamented about a lack of communication with parents about the delay.

"For the safety and concern of the children, an automated phone call should have been sent out to parents letting them know what was going on," Rhonda Whitehead Leaños wrote.

Hall County Superintendent Will Schofield sent an e-mail at 9:43 a.m. addressing the situation.

"I wanted to apologize to staff, students and their families for the weather situation this morning," he wrote. "... At around 6:30 a.m., the temperature dipped much more than expected and our area had a significant amount of black ice accompanied by traffic wrecks and delays. The safety of our staff and students is our paramount concern. We will examine our practices and determine how we can improve our decision-making process."

Gainesville City Schools officials kept buses operating on their regular routes Thursday morning.

Gainesville Superintendent Merrianne Dyer said there were no reports of buses having difficulty with the road conditions in the city.

She added that some of the buses were delayed on their routes to school because they were stuck in traffic due to other accidents on the road.

David Kimbrell, fire chief and Emergency Management director at Hall County Fire Services, described the weather Thursday morning as "a fluke." Emergency Management is a resource for school district leaders to discuss weather conditions and safety.

"This caught everyone in the region off guard," he said. "The weather service reports were that temperatures would not drop any lower than they dropped."