California health authorities have warned consumers that red leaf lettuce heads at three Southern California grocery store chains could be contaminated with Salmonella.

Oxnard, Calif.-based Fresh Choice Marketing recalled thirty 24-count cartons — 720 heads — said Ron Owens, a public information officer with the California Department of Public Health. The lot number was 530111.

No illnesses have been reported.

The lettuce was sold Oct. 20-Nov. 1 at Canton Food Co., Los Angeles, and at Cardenas Market and Numero Uno Market stores throughout Southern California, according to the state health department.

Identified only by the cartons they came in, the heads were unlabeled on store shelves. Store names and dates are the guides for consumers to follow, Owens said.

“This information should allow consumers to identify any potential red leaf lettuce in their possession that might be effected by the recall,” he said.

State health officials issued the warning Nov. 4.

The salmonella finding came from a U.S. Department of Agriculture test of a random sample from a produce wholesaler, Owens said. The sample came from Ontario, Calif., said Les Lee, general manager of Fresh Choice Marketing.

Lee said he initiated lab work on samples from the recalled lot the day after the state’s notice.

“I still had 20 boxes and proactively took a few test samples before I disposed of it,” he said. “Just to make sure everything was cleared. It all came out negative. Everything is clear as far as the FDA is concerned.”

Lee said the lot contained 63 cartons altogether.

While the lettuce is no longer being sold, CDPH investigators say consumers may still have product in their refrigerators and urge them to discard or return the lettuce to the store they bought it from.

UPDATED: Red leaf lettuce recalled in Southern California