CHICAGO (CBS) — For the second day in a row, more than a quarter of the children at an elementary school in northwest Indiana were not in school, as a highly contagious viral infection spread through the student body.

CBS 2’s Mike Puccinelli reports officials at Peifer Elementary School in Schererville have advised parents of children with symptoms of the infection – including vomiting or diarrhea – to keep their kids out of school for an extra day.

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Buses dropping kids off on Thursday were nowhere near full, due to a highly infectious viral outbreak.

The district has said norovirus likely is to blame for the quickly spreading illness, with more than 120 of the school’s 400 students missing class on Wednesday and Thursday.

“Twenty-seven percent of our population is significant, and it’s a concern,” Lake Central School Corporation assistant superintendent Al Gandolfi said.

He said the school hasn’t dealt with a norovirous outbreak in the past 5 to 7 years.

Parents whose kids were not ill were still concerned about sending their kids to school.

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“I am concerned, but the precautions that Peifer Elementary’s taking makes me feel more secure about her going to school today,” Wendy Holmes said. “She feels fine today. I don’t want her to miss out on her education.”

Officials used a special cleaning solution and brought in three times the usual custodians to sanitize the school on Wednesday.

“We were here into the late evening. We disinfected everything that a child touches, from a keyboard, to a doorknob, to every lunch table, to desks, to chairs,” Gandolfi said.

Some parents took their kids out of class, just to make sure they weren’t exposed, but Rob James said he trusts the district to do right by his daughter, Noelle, and the rest of the students.

“I wasn’t really concerned, after I heard of all the steps that the school district did; of all the cleaning overnight. I thought they got on top of it really well,” he said.

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Officials believe the virus spread from a child or teacher who came to school sick. They said the best way to prevent spreading the virus is to wash hands vigorously with soap and water.