Food and Drug Administration Commissioner Robert Califf said inspections found “shocking” conditions at Abbott’s infant formula plant in Michigan.

Califf said Abbott CEO Robert Ford told him the plant could resume production in early June, but the facility has to implement hundreds of steps before it can reopen to ensure food safety.

The FDA commissioner also said an investigation couldn’t conclude that unsanitary conditions led to four infants falling ill, two of whom died, but he called the confluence of events “highly unusual.”