NORFOLK - The school day at the Olive Day elementary started 20 to 25 minutes late Monday morning after a light ballast failure left the school's computer room with a foul odor.

The 8:50 a.m. incident coincided with parents and school buses dropping off students at the school at 232 Main St., causing a traffic backup in both directions, Fire Chief Coleman Bushnell said in a press release.

Police briefly closed the road to all but firefighters.

The ballast, in the school's Computer Learning Center, caught fire, just enough to activate the room's smoke detector but not the fire sprinklers, Bushnell said.

Firefighters used fans to clear the smoke and the odor, he said. Principal Linda Balfour said the building was evacuated.

The students who arrived first were kept outside, as if during a fire drill, she said. Other students stayed on school buses and in their parents' cars as they arrived.

"The children were absolutely great," Balfour said. "The staff really kicked it into high gear. They made sure we didn't have children in the hallways or bathrooms."

The school opened at 9:25 a.m., 20 to 25 minutes late, Balfour said.

Students in classes near the computer room initially were sent to the cafeteria, she said.

The computer teacher and one second-grade teacher "didn't use their classrooms for the first part of the morning" because the odor was so bad, she said.