Police officers in the US say they are becoming increasingly wary of eating fastfood snacks while on duty, as the number of reported cases of food-tampering cases aimed at the police is on the up.

Incidents of contamination with body fluids, marijuana and even cleaning fluids have been recorded and some police departments now issue lists warning officers not to eat in restaurants that have hired people that have been previously arrested or suspected as involved in criminal cases.

While employees are generally sacked when the incidents are discovered, in some states there is no criminal statute that prohibits spitting on food unless the fluid contains a communicable disease. For the companies involved in cases however, including fastfood giants Taco Bell, McDonald’s and Burger King, such cases can produce severe damage to public relations and sales.

Jim Pasco, executive director of the national Fraternal Order of Police, commented that the increase in cases is “consistent with the erosion of respect for authority figures.”