Of the 28 fourth-graders sickened by undercooked chicken Tuesday, 19 were back at New Brighton Elementary School yesterday.

Superintendent John Osheka said there is a minor risk of salmonella infection, and the district sent a letter home with pupils Tuesday asking parents to be alert for symptoms. Salmonella has a 12- to 48-hour incubation period, he said, so the district should know by midday today if there are any new cases.

Osheka said the cafeteria was serving chicken strips Tuesday, and they were popular enough that workers put an extra pan of 15 to 20 strips in the oven. But a worker set the timer wrong, then neglected to check the meat’s temperature when it came out.

The cafeteria is run by Metz Enterprises of Dallas, Luzerne County. Osheka said the company sent in executive chefs yesterday for in-service training. The employee at fault has been with Metz about 30 years and was not expected to be disciplined.