One person has died, and 10 people have been hospitalized due to an E. coli outbreak that has been linked to McDonald’s Quarter Pounders across more than 10 states. At least 49 people have fallen ill from the bacteria, according to the Centers for Disease Control and Prevention.

Most of the incidents have been in Colorado and Nebraska, and the CDC Outbreak Response and Prevention branch said it was carrying out a “fast-moving outbreak investigation” Tuesday.