A man in India’s Tamil Nadu state has been arrested for allegedly threatening a schoolgirl into mixing cow dung powder into food prepared for teachers, in retaliation for his wife’s dismissal from her job at the school.

The powder was allegedly added to food set aside for teachers and was not served to students, officials said as police identified the man as the husband of a former school worker who had been sacked from her job.

According to investigators, the man pressured the student to contaminate the food. The student initially told school authorities that she had put the substance into the meal herself, but later told police that she had acted on another person’s instructions.

The incident was uncovered after a teacher who tasted the morning meal noticed that it appeared to contain more turmeric than usual, which had changed the colour of the dish.

The cooks, however, said the food had been prepared normally and the yellow substance had not stained their hands.

Suspicion then turned to a student after school staff noticed a yellow mark on her hand.

The girl initially said it had come from cow dung while she was working at home.

Her parents denied the explanation, while other students reportedly said they had seen her buying cow dung powder from a shop.

The school informed education officials, who launched an investigation and directed the administration to report the matter to police.

During questioning, the student changed her account and said another person had told her to add the powder to the food.

The principal said the woman whose husband was arrested had previously been dismissed following complaints about hygiene practices, problems in food preparation and other issues.

A dispute subsequently developed between the former worker and a current employee, the principal said.

Police Inspector Veeram said authorities received a complaint on September 1 and arrested the suspect on September 2. He was then sent to judicial custody.