WASHINGTON (AP) — The United States Food and Drug Administration is warning against eating Uncle Ben’s rice products served at schools, restaurants, hospitals and other food service institutions after children in three states had skin reactions and other symptoms that were linked to the rice.

Mars Foodservices of Greenville, Mississippi, is recalling five- and 25-pound bags of the rice. The bags are mostly sold to food service establishments, but they are also available to consumers over the Internet.

Uncle Ben’s ready-to-eat, boxed, bagged and cup products in grocery stores are not linked to the illnesses and have not been recalled.

The FDA said that 34 students and four teachers in Katy, Texas, had experienced burning, itching rashes, headaches and nausea for 30 to 90 minutes after eating the rice on February 6. The symptoms eventually went away.

The agency said it is still investigating the Texas incident. But the agency said it found an excess of niacin, also known as vitamin B3, in Uncle Ben’s rice linked to similar reactions in 25 Illinois school children in December. That incident also prompted a recall, but the Texas illnesses were not related to those previously recalled lots.

The FDA said overexposure to niacin can cause skin reactions, and very large doses can cause indigestion and nausea.

The agency said it has not confirmed that the Texas incident was also caused by niacin, but the symptoms are similar. Another incident was reported in North Dakota in October, when three children in day care and one college student had skin reactions after eating an Uncle Ben’s rice product.

The recalled products are the five- and 25-pound bags of Uncle Ben’s flavour-infused rice, including roasted chicken flavour, garlic and butter flavour, Mexican flavour, saffron flavour, cheese flavour, Spanish flavour and Uncle Ben’s Rice Pilaf.

While Mars Foodservice has been working with the FDA and its buyers to get the rice out of lunch lines, agency officials said they are concerned that some consumers may be able to get the rice on the Internet or at warehouse-type retailers. As of Monday, several of the recalled products were still available on Amazon.com.