The US government is to step up its research into E-coli risks and prevention, the country's agriculture department has said.

The US Department of Agriculture is to spend US$5.5m on examining the prevalence of E-coli in fresh produce.

The study, headed by USDA researcher Rob Mandrell, will address where E. coli O157:H7 originates, how it survives on the plant, and what factors lead to an increase in produce-related outbreaks.

"This research will help producers identify the sources of E. coli O157:H7 and ways to avoid contamination," Agriculture Secretary Mike Johanns said. "Developing new research and prevention tactics for the grower will contribute to assuring produce safety for consumers."

The project comes amid growing concern over food safety in the US. Three people died and hundreds more fell ill in the past year after E-coli outbreaks related to bagged spinach.