More than 650 people have been sickened by a salmonella outbreak linked to onions imported from Mexico, the Centers for Disease Control and Prevention said Wednesday.

Across 37 states, 652 people have been reported sick, with 129 of them hospitalized. The full number of people affected is likely much higher, the CDC said, as many people recover from salmonella without being treated or tested for it.

The red, white and yellow onions were imported from Chihuahua, Mexico, and distributed by ProSource, and any onions labeled as being from Chihuahua, distributed by ProSource, or that don’t have a label should not be eaten and should be thrown away, the CDC said. Any surfaces or containers that may have touched the onions should also be washed thoroughly.

About 75 percent of sick people “ate or possibly ate raw onions or dishes likely containing raw onions before they became sick,” the CDC said.

The salmonella outbreak was identified in a sample of cilantro and lime from a condiment cup that had also contained onions and was collected from the home of someone who became sick.

The Food and Drug Administration said that ProSource had volunteered to recall onions it imported from July 1 to Aug. 27.

The CDC did not say how many onions may have been imported; Customs and Border Protection, which oversees imports into the United States, did not immediately respond to a request for comment. The CDC is investigating whether other onion suppliers may be linked to the outbreak.

ProSource told the CDC that onions were last imported Aug. 27 — but the onions can last for up to three months in storage “and may still be in homes and businesses,” the CDC said.

Many of the people who got sick said they became ill in August or September, according to CDC data. In August, the CDC alerted the public to a separate salmonella outbreak linked to red onions from a California company.

People with “severe” symptoms such as a fever higher than 102 degrees Fahrenheit, diarrhea, severe vomiting or signs of dehydration should call their health-care provider, the CDC said. Symptoms can start six hours to six days after consuming the contaminated food.

Salmonella are bacteria that cause an illness called salmonellosis, which can normally be treated without antibiotics. Salmonella cause about 1.35 million illnesses, 26,500 hospitalizations and 420 deaths in the United States annually, according to the CDC. Most people recover from symptoms in four to seven days.