Eleven students at a Franklin elementary school have confirmed cases of salmonella, and state health officials are investigating whether owl pellets used in a class project were the source of the bacterial infection.

Most of the sick students are fifth-graders at Jefferson Elementary School.

In a biology experiment, fifth-graders at the school pick out bones in owl pellets to identify animals, such as mice or chicks, the owls might have eaten. The experiment has been conducted by generations of students across the country.

Other possible sources of the infection include water from turtles in the classrooms and food consumed by fifth-graders at an event. The state Department of Public Health has ruled out school cafeteria food as a source.

The Health Department is interviewing students to determine their relationships and how they might have been exposed to the bacteria. It has also taken samples from the students and will test the owl pellets and turtles’ water.

It could take several months before results are known, especially since yesterday was the last day of school at Jefferson Elementary.