Twenty-one people in Maine and seven other states may have fallen ill after eating hamburgers possibly contaminated with E. coli bacteria, the Centers for Disease Control and Prevention said Wednesday.

CDC spokeswoman Lola Russell said three cases – two in New York and one in Florida – were confirmed as being linked to the ground beef. But the other 18 cases were possibly linked and under investigation.

No one has died, but Russell said she had no additional information on the cases.

Elizabeth, N.J.-based Topps Meat Co. on Tuesday announced a recall of boxes of frozen hamburgers it distributed.

The recall affects 331,582 pounds of frozen beef patties and 21 products that were distributed nationwide, the U.S. Department of Agriculture and Topps said.

Russell and USDA spokeswoman Amanda Eamich said the illnesses were reported in Connecticut, Florida, Indiana, Maine, New Jersey, New York, Ohio and Pennsylvania.

Officials were working to find the cause of the contamination.

“That investigation is still ongoing,” a Topps spokesman said. “Topps is going to fully cooperate with the USDA.” E. coli causes intestinal illness that generally clears up within a week for adults but can be deadly for the very young, the elderly and people with compromised immune systems.