The FBI searched two spinach packaging companies Wednesday for evidence in the nationwide E. coli outbreak that sickened 192 people.

Agents from the FBI and the Food and Drug Administration used warrants to search the San Juan Bautista plant of Natural Selection Foods LLC and a Growers Express plant in Salinas to determine whether they followed food safety procedures.

Federal health officials said early in their investigation that deliberate contamination was not suspected.

"We are investigating allegations that certain spinach growers and distributors may not have taken all necessary or appropriate steps to ensure that their spinach was safe before they were placed into interstate commerce," U.S. Attorney Kevin Ryan said in a statement.

The searches were the first indication that authorities suspect a crime may have been committed in the outbreak that led to at least one death and prompted the FDA to issue a two-week consumer warning on fresh spinach.

Natural Selection, which packages spinach sold under 34 brand names and supplies spinach to other food processors, was implicated in the E. coli outbreak after 11 bags of Dole brand baby spinach tested positive for the same bacteria strain found in people who feel ill after eating the leafy greens.