LOS ANGELES (Reuters) - Shares of Chipotle Mexican Grill Inc CMG.N lost more ground on Monday, after analysts cut stock price targets and raised doubts about whether the burrito chain can raise menu prices to offset higher costs.

FILE PHOTO: A Chipotle Mexican Grill is seen in Los Angeles, California, U.S. on April 25, 2016. REUTERS/Lucy Nicholson/File Photo

The chain’s stock shed nearly 13 percent of its value last week on reports of a Norovirus outbreak at a restaurant in Sterling, Virginia, and mice in a Dallas eatery. The shares fell 1.4 percent to $340.59 in afternoon trading on Monday after touching $336.65, their lowest intraday level since April 2013.

The moves in the stock reveal the fragility of Chipotle’s recovery from a sales-crushing string of food safety lapses in late 2015, when the chain was linked to E. coli, Salmonella and Norovirus outbreaks that sickened hundreds across the country.

Chipotle’s stock flirted with $750 prior to those incidents.

CFRA Research analyst Tuna Amobi on Monday chopped his 12-month price target by more than a third, reducing it by $190 to $350 per share, and downgraded Chipotle shares to “hold” from “buy”.

Amobi cut 2017 earnings per share estimates by 46 cents to $8 and took his 2018 target down 25 cents to $11.68, citing the latest Norovirus and rodent headlines.

“We infer major setbacks to (Chipotle’s) ongoing recovery efforts after (2015) health-related concerns on virus outbreaks at several locations that precipitated a steep and protracted downturn in customer traffic,” Amobi wrote.

Credit Suisse analyst Jason West cut Chipotle’s price target to $325 from $425.

“We believe the recent negative headlines may delay price increases. We now assume no additional menu pricing in 2018,” wrote West, who added that ongoing challenges could also force it open fewer restaurants.

The Loudoun County Health Department said on Monday more than 135 people reported falling ill after eating at the Sterling, Virginia, Chipotle restaurant from July 13 to 16. Two of those diners tested positive with the same strain of Norovirus, officials said.

“The specific source of the Norovirus has not yet been identified,” said Dr. David Goodfriend, director of the health department.

The restaurant was briefly closed last week for a deep cleaning, and no illness has been reported since it reopened on Wednesday.

Norovirus is the leading cause of illness from contaminated food in the United States. It can spread from person to person, as well as through food prepared by an infected person.

Chipotle will report quarterly results after the market close on Tuesday.