Chipotle will pay the largest fine ever for a food safety case over the poisoning of more than 1,100 customers across the US with the highly infectious norovirus between 2015 and 2018.

The Justice Department on Tuesday deferred criminal prosecution after the Mexican grill agreed to pay a $25m fine and implement a food safety program.

The Newport Beach, California-based chain was charged with adulterating food while held for sale after shipment in interstate commerce after outbreaks in Los Angeles, Simi Valley, Boston, Virginia and Ohio of contagious pathogens that cause severe diarrhoea, vomiting and abdominal cramping.

In a statement to The Independent, Chipotle CEO Brian Niccol said the agreement with the Justice Department was an acknowledgement of how seriously the company takes food safety.

"[This] is an opportunity to definitively turn the page on past events," Mr Niccol said.

Following the negative publicity from the outbreaks, Mr Niccol was brought in to revive the chain in February 2018. He moved the headquarters from Denver, Colorado to southern California, revamped their marketing, streamlined the menu, and implemented policies to restore customer confidence in the chain's food safety.

US Attorney Nick Hanna said the record $25m penalty, combined with the millions the company already spent to upgrade food safety, should protect Chipotle customers and remind others to improve standards.

"Chipotle failed to ensure that its employees both understood and complied with its food safety protocols, resulting in hundreds of customers across the country getting sick," Mr Hanna said.

As part of the deferred prosecution agreement, Chipotle admitted to at least five incidents around the country stemming from employees' failure to follow food safety policies, "including the policy requiring the exclusion of restaurant employees who were sick or recently had been sick, as well as a failure by restaurant employees to hold food at appropriate temperatures to prevent and control for the growth of foodborne pathogens."

Chipotle's admissions included reports from store-level employees, many teenagers and young adults, saying they felt pressured to continue working while feeling sick because they didn't want to let their teammates down or couldn't find people to cover shifts.