The Centers for Disease Control and Prevention and other federal agencies are investigating an E. coli outbreak linked to McDonald’s Quarter Pounders, sending McDonald’s stock down 7% in after-hours trading.

The Centers for Disease Control and Prevention (CDC) issued a food safety alert on Tuesday which said an E. coli outbreak linked to McDonald’s burgers has led to one death and ten hospitalizations. “Most people in this outbreak are reporting eating the Quarter Pounder hamburger at McDonald’s before becoming sick,” the alert read.

McDonald’s Quarter Pounder hamburgers have been linked to an E. coli outbreak that has sickened at least 49 people and killed one, according to the Centers for Disease Control and Prevention.Illnesses have been reported in 10 states,