Italian police have seized 85,000 tons of olives from previous years’ harvests covered with a chemical aimed at making them more colorful, authorities said Wednesday.

Authorities charged 19 people in the incident for using banned chemicals and planning to sell food products containing dangerous substances. Copper sulfate is a commonly used pesticide that is allowed in most jurisdictions, but in this case the chemical was applied directly to the olives leading to an unsafe concentration, authorities said. Copper sulfate can have some toxic effects when exposed to large quantities. The coloring initially evaded police detection because copper sulfate isn’t typically used for coloring and, therefore, authorities don’t test for it.

Police also said they were investigating 7,000 tons of olive oil purveyors falsely claimed was made in Italy. Tests showed the olive oil was actually from Syria and Turkey.

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Write to Justin Worland at justin.worland@time.com.