How did Camden preschoolers drink contaminated milk? Here’s what we know.

The Camden City School District has stopped serving milk to all its students after at least 53 children in four schools were medically treated Wednesday after consuming milk contaminated with a sanitizer.

After drinking the milk — distributed at the Camden Early Childhood Development Center, the Riletta T. Cream Early Childhood Development Center, the Yorkship Family School, and the Veterans Memorial School — the children, who ranged in age from 3 to 5 years old, were taken to Our Lady of Lourdes Hospital and Cooper University Hospital, or treated on site.

The students and one staff member were treated and released, with primary symptoms being vomiting.

Here’s an update on what else we know:

The half-pint cartons containing 1% low-fat milk with a sell date of April 11 were distributed to Camden schools by Aramark, the district’s Philadelphia-based food service provider. The milk was manufactured by Guida’s Dairy in New Britain, Conn., and distributed by Cream-O-Land.

Guida’s Dairy believes the contamination was limited and was caused when the food-grade sanitizer, used to clean the cartons, was inadvertently introduced into machines during milk production. The cartons were sealed and shipped out with the milk.

The school district pulled 95 cartons from its inventory. Milk from this batch was found at four locations, but it is unknown whether the milk was contaminated at each of these locations.

The colorless substance is known as Vortexx and is usually diluted in water. The nontoxic substance is used to sanitize certain surfaces of airtight and sealed packages containing foods and beverages to prevent mold and bacteria.

The Camden school district said that out of an abundance of caution, it has directed its food services department not to serve any milk products until investigations are completed.

According to the Camden County Health Department, the contamination has been limited to Camden city public schools, which serves about 5,200 students, and there have been no reports from other districts.

Cherry Hill Public Schools has pulled all plain milk from its buildings and will not be providing it through at least Friday. (Students can get chocolate milk, juice, or water). It also received milk provided by Aramark, but not from the same batch as the milk served in Camden.

Collingswood Public Schools, supplied with the same brand of milk, has replaced its batch with a different brand, although it had no reports of adverse reactions related to milk consumption there. The district said it will not accept any shipments of milk produced by Guida until the Camden County Health Department completes its investigation.

No, it is not available at retail outlets for consumer purchase. Guida said about 1,000 cartons from the batch were distributed in New Jersey, to schools and institutions.

The New Jersey Department of Health notified local health authorities on Thursday that Guida’s Dairy advised all its institutional customers to dispose of any remaining half-pint cartons of its 1% low-fat milk.

If you or someone you know may have been exposed or ingested this milk, please call the Camden County Health Department at 856-549-0530.