Quong Hop & Co. failed to maintain its Airport Boulevard plant in a sanitary condition, didn’t stop pests from entering food-processing areas and didn’t ensure that food was protected from contamination, said John Wilson, a San Mateo County deputy district attorney.

There was no evidence, however, that anyone got sick from eating products made by Quong Hop, which does business under names including Soy Deli, Soy Fresh, Raquel’s and Melissa’s, Wilson said.  The violations were found during inspections in recent years by the state Department of Public Health, Wilson said.

In 2007, the company recalled a number of tofu products after detecting the bacteria listeria monocytogenes in them and in the plant. Listeria monocytogenes can cause serious and sometimes fatal infections in young children, frail or elderly people and others with weakened immune systems.

An inspection at the facility on Wednesday did not uncover additional violations, authorities said.