The New York Times reports that federal investigators have opened a criminal investigation into accusations that some California spinach growers and distributors failed to take adequate measures to ensure that their spinach was safe before selling it.

Yesterday, agents of the FBI and the Office of Criminal Investigations in the FDA carried out search warrants at Natural Selection Foods of San Juan Bautista and Growers Express of Salinas.

Natural Selection, a large distributor of fresh produce, had previously recalled its packages of fresh spinach.