A nationwide cyclospora outbreak linked to shredded iceberg lettuce has expanded to nine states, with nearly 2,000 illnesses reported.

The CDC said the outbreak is the largest of its kind in the U.S. this year, though no deaths have been reported.

Health officials have focused on lettuce supplied by Taylor Farms from its facility in Mexico, which led to a recall and the removal of affected products from restaurants.

Mexican officials said tests from the facility were negative, but the FDA continues to investigate the company as the likely source, CNBC has reported.

Regulators are also examining a separate cyclospora outbreak tied to an unknown food source as they work to contain the spread.