The Illinois Department of Public Health issued a warning Thursday, saying 100 people have contracted Salmonella linked to illegally manufactured Mexican-style cheeses.

Health departments in Cook, DuPage, Boone, Fayette, Kane, Lake, LaSalle, Macon, Marion, McHenry, Vermillion, Washington and Will counties have reported about 100 cases of Salmonella believed to be associated with the cheese since July 2012, according to a statement from the department.

IDPH is working to identify the manufacturer of the contaminated cheese, according to the department.

Many cases have reported consuming Mexican-style cheese obtained from worksites, including factories, and at train stations, from street vendors and from relatives and friends, the department said. The cheese is not labeled and is often wrapped in aluminum foil.