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BILLERICA, Mass. — A Chipotle store in Massachusetts was temporarily closed due to concerns that several employees may have contracted the norovirus.

The company said Tuesday that four workers reported not feeling well, spurring Chipotle to shut the doors at its restaurant in Billerica — a town about 20 miles outside of Boston, where health officials suspected Chipotle customers of contracting norovirus in December last year.

The store was closed for a “full sanitation,” Chipotle spokesperson Chris Arnold said Tuesday. “We do not know know if the employees are ill with norovirus and no customers’ illnesses are connected to this restaurant. Any employees who reported feeling ill will be tested and held out of the restaurant until they fully recover.”

Scott Zoback, spokesman for the Massachusetts Department of Public Health, said state health officials do not yet know whether or not the employees are infected with norovirus, and the health department was awaiting updates from officials in Billerica.

Zoback also said that reports of norovirus have not been connected with eating at the Chipotle in Billerica.

Chipotle was recently subpoenaed by a federal grand jury over a norovirus outbreak in California. The company said in a public filing that the California incident was isolated and that it will cooperate fully with the federal investigation.

That followed a months-long E. coli outbreak that was connected to eating at Chipotle restaurants in multiple states.

Norovirus is highly contagious, causing about 20 million cases in the United States each year.

–CNN’s John Newsome contributed to this report.