Fresh salsa and guacamole can pose significant food safety risks, according to a new study.

Because they often contain diced raw produce, are often made in large batches and are often poorly refrigerated, fresh salsa and guacamole can be prone to contamination that can cause foodborne illness, according to a study published in the journal Foodborne Pathogens and Disease.

“The safety of salsa and guacamole is increasingly important as these foods gain popularity,” according to the study. “Fresh salsa and guacamole require careful preparation and storage.”

The study’s authors reviewed all reports of food safety outbreaks between 1973 and 2008 involving salsa or guacamole.

They turned up 136 outbreaks in which salsa or guacamole was reported as a possible vehicle. Those outbreaks resulted in 5,658 illnesses.

About 24% of the outbreaks were caused by norovirus and 19% by salmonella. Eighty-four percent of the outbreaks were caused by foods prepared in restaurants or delis. Of those, 19% reported ill workers, and 29% improper storage, as possible causes of the outbreaks.