In opening a criminal investigation into two produce companies involved in the contaminated spinach outbreak, federal agents are following a script first written a decade ago to hold companies responsible for mass food poisoning.

In 1996, authorities secured the first criminal conviction in a food poisoning case when juice-maker Odwalla Inc. was heavily fined for tainted apple juice that killed a baby. That was followed by a case against Sara Lee Corp. five years later, which led to a fine for tainted hot dogs and lunch meats that killed 15 people.