Chipotle says it has been subpoenaed by a federal grand jury over a norovirus incident at one of its Southern California restaurants.  The burrito chain says the subpoena is connected to a criminal investigation into an "isolated norovirus incident" at a Simi Valley restaurant last August. 

Chipotle says it intends to fully cooperate in the investigation.  Dozens of people around the country have been sickened by E. coli and norovirus outbreaks at Chipotle restaurants in several states.  The company also said that a norovirus incident at a Boston-area Chipotle last month would lead to a 14-percent decline in fourth-quarter sales. 

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