As the mysterious E. coli outbreak continues to unfold in Germany, U.S. public health officials are boosting surveillance of produce from Germany and Spain. Fresh tomatoes, cucumbers, and lettuce remain suspects for the cause of the outbreak, but over the weekend authorities in Germany added local bean sprouts to the warning list.

A spokesperson for the Food and Drug Administration said Sunday the U.S. has received no shipments of sprouts or sprout seeds from Germany or Spain since at least last October.

The agency says it is increasing surveillance to include all fresh tomatoes, cucumbers, lettuce–including salad mixes and prepared salads — and all sprouts and sprout seeds from Germany and Spain.

The U.S. imports a relatively small amount of fresh produce from European countries, particularly at this time of year, when there is ample supply domestically and from Central and South America.

According to the most recent U.S. Department of Agriculture trade data, the U.S. imports approximately around $420 million in fresh fruits, vegetables, and vegetable seeds annually from the EU.  In 2010, the U.S. imported around $15 billion worth of these products overall.