As the search drags on for the source of the recent salmonella outbreak involving certain kinds of tomatoes, the number of people sickened has gone up.

The Centers for Disease Control said Monday that the total is now 277 people in 28 states and the District of Columbia. The outbreak of the Saintpaul strain of salmonella dates back to April 10.

Meanwhile, federal officials have announced two more states (New Mexico and Indiana) have been cleared in the investigation, as well as part of Mexico (Baja California).

One possible lead in the case is nine illnesses that have been linked to an unnamed restaurant chain.

The FDA believes the salmonella contamination likely started in the two major tomato-producing areas of Florida or Mexico.

Consumers are advised to avoid any fresh Roma, plum or standard round tomatoes that are not from the 37 states (see the list below) that have been excluded as the source of the outbreak. The FDA has said since the beginning of the scare that cherry and grape tomatoes and tomatoes still attached to the vine are fine.

Most major restaurant chains, including Wendy’s, Burger King and McDonald’s are restocking tomatoes, after pulling them earlier this month.

For the time being, the FDA advises consumers to eat tomatoes grown only in the following states: Alabama, Alaska, Arkansas, California, Colorado, Delaware, Florida (counties of: Jackson, Gadsden, Leon, Jefferson, Madison, Suwannee, Hamilton, Hillsborough, Polk, Manatee, Hardee, DeSoto, Sarasota, Highlands, Pasco, Sumter, Citrus, Hernando, Charlotte — but only with a certificate from the Florida Department of Agriculture and Consumer Services), Georgia, Hawaii, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, New Hampshire, New Jersey, New York, Nebraska, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, and Wisconsin.

For more information, read the CDC’s FAQ on Salmonella in tomatoes:
http://www.cdc.gov/salmonella/saintpaul/faq.html