Students of a New Jersey preschool and kindergarten center were sent to the hospital Wednesday after they were served milk cartons filled with sanitizer, officials said.

An investigation into “a possible contamination of milk” at the Early Childhood Development Center revealed that milk cartons were filled with sanitizer used to clean machines that fill the cartons, according to the Camden City School District.

The Camden Schools Early Childhood Development Center in Camden, N.J.The Camden City schools Early Childhood Development Center in Camden, N.J.Google maps

The cartons were sealed and shipped out before anyone noticed, the district said.

An unspecified number of students were served the contaminated milk cartons. The district said the sanitizer is non-toxic, and no students were sick, but they were sent to a hospital “as a precaution.”

“We pulled all milk today and NO milk will be served until the investigation is completed,” the district said.