Foster Farms raw chicken products made at three California sites may have sickened nearly 300 people in 18 states, according to a public health alert issued Monday by U.S. Department of Agriculture officials.

JoNel Aleccia of NBC News and Lynne Terry of The Oregonian report that at least 278 illnesses caused by salmonella Heidelberg linked to the chicken brand have been reported, mostly in California, according to the USDA’s Food Safety and Inspection Service. The products were distributed mainly to outlets in California, Oregon and Washington state. 

The notice follows an outbreak earlier this year traced to Foster Farms raw chicken in which 134 people in 13 states became ill, but it appears to be a separate, new incident, said Barbara Reynolds, a spokeswoman for the Centers for Disease Control and Prevention. That outbreak, which was declared over in July, sickened 40 people in Oregon and 57 in Washington state and sent 33 patients to the hospital.

Neither agency could provide many details about the latest outbreak because of limited staffing caused by a week-long government shutdown.

Illnesses were linked to the Foster Farm brand through epidemiologic, laboratory and trace-back methods, FSIS said. But health officials were unable to tie the illnesses to a specific product or a specific production period. They said that the products bear one of three establishment numbers inside a USDA mark of inspection or elsewhere on the package. The numbers are: P6137, P6137A and P7632.

The USDA allows producers to sell raw poultry with a nearly 10 percent incidence rate of salmonella. Foster Farms says it’s always met that standard. It is not issuing a recall.

Foster Farms officials said in a statement that the company has been collaborating with FSIS and CDC to eradicate salmonella Heidelberg at its sites and has retained national experts to “assess current practices and identify opportunities for further improvement.”