April 5 in History: Ground-Up Glass Found in Brooklyn Food 
Many types of food were found to be tampered with in this food-safety scare from April 5, 1918.
Some of the unsanitary conditions that could potentially contaminate food during production may be too much for most of us to consider when choosing a candy bar from the local bodega, but imagine if someone was intentionally tampering with the product intending to injure anyone that ate it. This seemed to be the situation in Brooklyn 98 years ago, as a crisis of ground glass being found in food was beginning to take shape.
In this article from the New York Tribune outlines the cases around the city where glass fragments had been found in food. Either glass or pieces of metal wire had been found in bread, rolls, crullers, candy, chewing gum, salted almonds, frankfurters, and even a sample of sugar.
State and Federal agencies were gathering together to track down the source of the glass that had made its way into such a variety of products. The Department of Justice, New York police, the Food Board, and the Brooklyn Food Protection Agency were all attempting to solve the malicious act.
Given the tense wartime relations with Germany, the Brooklyn Food Protection Agency ordered that Brooklyn bakeries should fire all German immigrants, and if any "enemy aliens" were employed at food facilities, they should ensure that there was no way for them to introduce inappropriate ingredients during food production.
Two days later, the Food Board would announce more glass had been discovered, with cases showing up in Hoboken and Waterbury, Connecticut.