WASHINGTON — The Agriculture Department says three California poultry processing facilities linked to a salmonella outbreak in raw chicken can stay open, for now.

In a statement Thursday, the USDA said Foster Farms, which owns the facilities in Fresno and Livingston, Calif., has made “immediate substantive changes to their slaughter and processing to allow for continued operations.”

The department threatened earlier this week to shut down the plants if Foster Farms did not prove it had made enough changes. Sampling by the USDA in September showed that raw chicken processed by those facilities included strains of salmonella that were linked to the outbreak that has sickened 278 people in 17 states.

USDA said inspectors will monitor the company’s improvements and “continue intensified sampling” of Foster Farms meat for the next three months.

In a Monday letter to Foster Farms, USDA said the positive samples coupled with the illnesses suggest the sanitary conditions at the facility “could pose a serious ongoing threat to public health.”

The outbreak, which has been going on since March, has had a high rate of hospitalizations. The Centers for Disease Control and Prevention said 42 percent of victims were hospitalized, about double the normal rate.